Fix more unused variables and enable unused-but-set-variable errors.

Add -Werror=unused-but-set-variable to our default compiler flags and fix

```
epan/dissectors/packet-dcerpc-frsrpc.c:709:10: error: variable 'nb_chunk' set but not used [-Werror,-Wunused-but-set-variable]
        guint32 nb_chunk = 0;
                ^
```

```
epan/dissectors/packet-dcom-oxid.c:175:13: error: variable 'u32ItemIdx' set but not used [-Werror,-Wunused-but-set-variable]
    guint32 u32ItemIdx;
            ^
```

```
epan/dissectors/packet-l2tp.c:1775:104: error: parameter 'ccid' set but not used [-Werror,-Wunused-but-set-parameter]
static int dissect_l2tp_ericsson_avps(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree, guint32 ccid)
                                                                                                       ^
```

```
epan/dissectors/packet-ldp.c:1922:19: error: variable 'ix' set but not used [-Werror,-Wunused-but-set-variable]
    guint8        ix;
                  ^
```

```
epan/dissectors/packet-nas_5gs.c:4757:14: error: variable 'curr_len' set but not used [-Werror,-Wunused-but-set-variable]
    guint i, curr_len;
             ^
```

```
epan/dissectors/packet-per.c:1769:6: error: variable 'extension_addition_entries' set but not used [-Werror,-Wunused-but-set-variable]
        int extension_addition_entries;
            ^
```

```
epan/dissectors/packet-rtitcp.c:618:11: error: variable 'messages_count' set but not used [-Werror,-Wunused-but-set-variable]
    guint messages_count, offset;
          ^
```

```
epan/dissectors/packet-tcp.c:2130:9: error: variable 'ackcount' set but not used [-Werror,-Wunused-but-set-variable]
    int ackcount;
        ^
epan/dissectors/packet-tcp.c:3317:12: error: variable 'nbOptionsChanged' set but not used [-Werror,-Wunused-but-set-variable]
    guint8 nbOptionsChanged = 0;
           ^
```

```
epan/dissectors/packet-zbee-zcl-se.c:11802:15: error: variable 'i' set but not used [-Werror,-Wunused-but-set-variable]
    for (gint i = 0; tvb_reported_length_remaining(tvb, *offset) >= 5; i++) {
              ^
```

```
ui/iface_lists.c:142:23: error: variable 'linktype_count' set but not used [-Werror,-Wunused-but-set-variable]
    gint              linktype_count;
                      ^
```

```
ui/voip_calls.c:456:15: error: variable 'item_num' set but not used [-Werror,-Wunused-but-set-variable]
    guint     item_num;
              ^
```

```
file.c:572:17: error: variable 'count' set but not used [-Werror,-Wunused-but-set-variable]
        guint32 count             = 0;
                ^
```

```
file.c:3667:24: warning: cast from 'const unsigned char *' to 'unsigned char *' drops const qualifier [-Wcast-qual]
        pd = (guint8 *)ws_mempbrk_exec(pd, buf_end - pd, pattern, &c_char);
                       ^
```

```
ui/qt/io_graph_dialog.cpp:1932:60: error: variable 'mavg_right' set but not used [-Werror,-Wunused-but-set-variable]
    unsigned int mavg_in_average_count = 0, mavg_left = 0, mavg_right = 0;
                                                           ^
```

```
ui/qt/stats_tree_dialog.cpp:166:9: error: variable 'node_count' set but not used [-Werror,-Wunused-but-set-variable]
    int node_count = 0;
        ^
```

```
ui/qt/models/profile_model.cpp:1142:13: error: variable 'entryCount' set but not used [-Werror,-Wunused-but-set-variable]
        int entryCount = 0;
            ^
```

9 files changed, 9 insertions, 30 deletions

diff --git a/epan/dissectors/packet-dcerpc-frsrpc.c b/epan/dissectors/packet-dcerpc-frsrpc.c
index 5d506f487b..b733ae200b 100644
--- a/epan/dissectors/packet-dcerpc-frsrpc.c
+++ b/epan/dissectors/packet-dcerpc-frsrpc.c
@@ -663,7 +663,7 @@ frsrpc_dissect_struct_CommPktChunk(tvbuff_t *tvb _U_, int offset _U_, packet_inf
 		item = proto_tree_add_item(parent_tree, hf_index, tvb, offset, -1, TRUE);
 		tree = proto_item_add_subtree(item, ett_frsrpc_frsrpc_CommPktChunk);
 	}
-	
+
 	offset = frsrpc_dissect_element_CommPktChunk_type(tvb, offset, pinfo, tree, di, drep, &type);
 	offset = frsrpc_dissect_element_CommPktChunk_data(tvb, offset, pinfo, tree, di, drep, &type);
 	for (i=0; frsrpc_frsrpc_CommPktChunkType_vals[i].strptr; i++) {
@@ -706,14 +706,13 @@ frsrpc_dissect_enum_CommPktCommand(tvbuff_t *tvb _U_, int offset _U_, packet_inf
 static int
 frsrpc_dissect_struct_frsrpc_CommPktChunkCtr(tvbuff_t *tvb, int offset, packet_info *pinfo, proto_tree *tree, dcerpc_info* di, guint8 *drep _U_, int hf_index, guint32 param _U_)
 {
-	guint32 nb_chunk = 0;
 	guint32 remaining = tvb_reported_length_remaining(tvb, offset);
 	int align_status = di->no_align;
 	if (remaining > 0) {
 		proto_item *item = proto_tree_add_item(tree, hf_index, tvb, offset, -1, TRUE);
 		proto_tree *subtree = proto_item_add_subtree(item, ett_ChunkCtr);
 		di->no_align = 1;
-		for(nb_chunk = 0; remaining > 0; nb_chunk++) {
+		while (remaining > 0) {
 			offset = frsrpc_dissect_struct_CommPktChunk(tvb, offset, pinfo, subtree, di, drep, hf_CommPktChunk, param);
 			remaining = tvb_reported_length_remaining(tvb, offset);
 		}
diff --git a/epan/dissectors/packet-dcom-oxid.c b/epan/dissectors/packet-dcom-oxid.c
index 09bd914911..0accf0e21d 100644
--- a/epan/dissectors/packet-dcom-oxid.c
+++ b/epan/dissectors/packet-dcom-oxid.c
@@ -172,7 +172,6 @@ dissect_oxid_resolve_oxid2_rqst(tvbuff_t *tvb, int offset,
 {
     guint16 u16ProtSeqs;
     guint32 u32ArraySize;
-    guint32 u32ItemIdx;
 
 
     offset = dissect_dcom_ID(tvb, offset, pinfo, tree, di, drep,
@@ -184,11 +183,9 @@ dissect_oxid_resolve_oxid2_rqst(tvbuff_t *tvb, int offset,
     offset = dissect_dcom_dcerpc_array_size(tvb, offset, pinfo, tree, di, drep,
                         &u32ArraySize);
 
-    u32ItemIdx = 1;
     while (u32ArraySize--) {
         offset = dissect_dcom_WORD(tvb, offset, pinfo, tree, di, drep,
                             hf_oxid_protseqs, &u16ProtSeqs);
-        u32ItemIdx++;
     }
 
     return offset;
diff --git a/epan/dissectors/packet-l2tp.c b/epan/dissectors/packet-l2tp.c
index 08e6b1316b..fd2181d3cd 100644
--- a/epan/dissectors/packet-l2tp.c
+++ b/epan/dissectors/packet-l2tp.c
@@ -1772,7 +1772,7 @@ static int dissect_l2tp_ericsson_tei_sc_map(tvbuff_t *tvb, proto_tree *parent_tr
     return offset;
 }
 
-static int dissect_l2tp_ericsson_avps(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree, guint32 ccid)
+static int dissect_l2tp_ericsson_avps(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree, guint32 ccid _U_)
 {
     int offset = 0;
     int         avp_type;
@@ -1813,8 +1813,6 @@ static int dissect_l2tp_ericsson_avps(tvbuff_t *tvb, packet_info *pinfo _U_, pro
     offset += 2;
     avp_len -= 2;
 
-    ccid++;
-
     switch (avp_type) {
     case ERICSSON_MSG_TYPE:
         proto_tree_add_item_ret_uint(l2tp_avp_tree, hf_l2tp_ericsson_msg_type, tvb, offset, 2, ENC_BIG_ENDIAN, &msg_type);
diff --git a/epan/dissectors/packet-ldp.c b/epan/dissectors/packet-ldp.c
index a8758d6e23..eb1bcfcaa2 100644
--- a/epan/dissectors/packet-ldp.c
+++ b/epan/dissectors/packet-ldp.c
@@ -1919,11 +1919,10 @@ static void
 dissect_tlv_mac(tvbuff_t *tvb, packet_info *pinfo, guint offset, proto_tree *tree, int rem)
 {
     proto_tree   *val_tree;
-    guint8        ix;
 
     val_tree=proto_tree_add_subtree(tree, tvb, offset, rem, ett_ldp_tlv_val, NULL, "MAC addresses");
 
-    for(ix=1; rem >= 6; ix++, offset += 6, rem -= 6) {
+    for(; rem >= 6; offset += 6, rem -= 6) {
         proto_tree_add_item(val_tree, hf_ldp_tlv_mac, tvb, offset, 6, ENC_NA);
     }
     if (rem)
diff --git a/epan/dissectors/packet-nas_5gs.c b/epan/dissectors/packet-nas_5gs.c
index 3a5c066d3e..57404de50a 100644
--- a/epan/dissectors/packet-nas_5gs.c
+++ b/epan/dissectors/packet-nas_5gs.c
@@ -4754,9 +4754,8 @@ de_nas_5gs_sm_mapped_eps_b_cont(tvbuff_t *tvb, proto_tree *tree, packet_info *pi
     proto_tree * sub_tree, *sub_tree1;
     guint32 num_cont, length, opt_code, num_eps_parms, param_id;
     proto_item * item;
-    guint i, curr_len;
+    guint i;
 
-    curr_len = len;
     curr_offset = offset;
     num_cont = 1;
 
@@ -4785,12 +4784,10 @@ de_nas_5gs_sm_mapped_eps_b_cont(tvbuff_t *tvb, proto_tree *tree, packet_info *pi
         /* EPS bearer identity */
         proto_tree_add_item(sub_tree, hf_nas_5gs_sm_mapd_eps_b_cont_id, tvb, curr_offset, 1, ENC_BIG_ENDIAN);
         curr_offset++;
-        curr_len--;
 
         /* Length of Mapped EPS bearer context*/
         proto_tree_add_item_ret_uint(sub_tree, hf_nas_5gs_sm_length, tvb, curr_offset, 2, ENC_BIG_ENDIAN, &length);
         curr_offset += 2;
-        curr_len -= 2;
 
         /*  8     7     6     5     4     3     2     1          */
         /* operation code | spare | E | number of EPS params     */
@@ -4810,7 +4807,6 @@ de_nas_5gs_sm_mapped_eps_b_cont(tvbuff_t *tvb, proto_tree *tree, packet_info *pi
 
         }
         curr_offset++;
-        curr_len--;
         i = 1;
 
         /* EPS parameters list */
@@ -4823,12 +4819,10 @@ de_nas_5gs_sm_mapped_eps_b_cont(tvbuff_t *tvb, proto_tree *tree, packet_info *pi
             proto_tree_add_item_ret_uint(sub_tree1, hf_nas_5gs_sm_mapd_eps_b_cont_param_id, tvb, curr_offset, 1, ENC_BIG_ENDIAN, &param_id);
             proto_item_append_text(item, " - %s", val_to_str_const(param_id, nas_5gs_sm_mapd_eps_b_cont_param_id_vals, "Unknown"));
             curr_offset++;
-            curr_len--;
 
             /*length of the EPS parameter contents field */
             proto_tree_add_item_ret_uint(sub_tree1, hf_nas_5gs_sm_length, tvb, curr_offset, 1, ENC_BIG_ENDIAN, &length);
             curr_offset++;
-            curr_len--;
 
             proto_item_set_len(item, length + 2);
             /*content of the EPS parameter contents field */
@@ -4858,7 +4852,6 @@ de_nas_5gs_sm_mapped_eps_b_cont(tvbuff_t *tvb, proto_tree *tree, packet_info *pi
                 break;
             }
             curr_offset +=length;
-            curr_len -= length;
             i++;
             num_eps_parms--;
         }
diff --git a/epan/dissectors/packet-per.c b/epan/dissectors/packet-per.c
index 8a540b8fa3..1f136e2645 100644
--- a/epan/dissectors/packet-per.c
+++ b/epan/dissectors/packet-per.c
@@ -1766,7 +1766,6 @@ dissect_per_choice(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *
 {
 	gboolean /*extension_present,*/ extension_flag;
 	int extension_root_entries;
-	int extension_addition_entries;
 	guint32 choice_index;
 	int i, idx, cidx;
 	guint32 ext_length = 0;
@@ -1790,7 +1789,6 @@ DEBUG_ENTRY("dissect_per_choice");
 
 	/* count the number of entries in the extension root and extension addition */
 	extension_root_entries = 0;
-	extension_addition_entries = 0;
 	for (i=0; choice[i].p_id; i++) {
 		switch(choice[i].extension){
 			case ASN1_NO_EXTENSIONS:
@@ -1798,7 +1796,6 @@ DEBUG_ENTRY("dissect_per_choice");
 				extension_root_entries++;
 				break;
 			case ASN1_NOT_EXTENSION_ROOT:
-				extension_addition_entries++;
 				break;
 		}
 	}
diff --git a/epan/dissectors/packet-rtitcp.c b/epan/dissectors/packet-rtitcp.c
index c8408c309a..d58ae19702 100644
--- a/epan/dissectors/packet-rtitcp.c
+++ b/epan/dissectors/packet-rtitcp.c
@@ -615,19 +615,16 @@ static guint16 dissect_control_message(proto_tree *rtitcp_tree, tvbuff_t *tvb, p
 
 /* This function dissects all the control messages found */
 static guint dissect_rtitcp_control_protocol(proto_tree *rtitcp_tree, tvbuff_t *tvb, packet_info *pinfo) {
-    guint messages_count, offset;
+    guint offset;
     guint16 msg_length;
     guint32 tvb_len;
 
     offset = 0;
     tvb_len = tvb_reported_length(tvb);
 
-    messages_count = 0;
-
     while (offset < tvb_len) {
         msg_length = dissect_control_message(rtitcp_tree, tvb, pinfo, offset);
         offset += msg_length;
-        ++messages_count;
     }
 
     return offset;
diff --git a/epan/dissectors/packet-tcp.c b/epan/dissectors/packet-tcp.c
index 3c79de5d10..db5ec84197 100644
--- a/epan/dissectors/packet-tcp.c
+++ b/epan/dissectors/packet-tcp.c
@@ -2127,7 +2127,6 @@ tcp_analyze_sequence_number(packet_info *pinfo, guint32 seq, guint32 ack, guint3
     tcp_unacked_t *ual=NULL;
     tcp_unacked_t *prevual=NULL;
     guint32 nextseq;
-    int ackcount;
 
 #if 0
     printf("\nanalyze_sequence numbers   frame:%u\n",pinfo->num);
@@ -2673,7 +2672,6 @@ finished_checking_retransmission_type:
 
     /* remove all segments this ACKs and we don't need to keep around any more
      */
-    ackcount=0;
     prevual = NULL;
     ual = tcpd->rev->tcp_analyze_seq_info->segments;
     while(ual) {
@@ -2698,7 +2696,6 @@ finished_checking_retransmission_type:
         }
 
         /* This segment is old, or an exact match.  Delete the segment from the list */
-        ackcount++;
         tmpual=ual->next;
 
         if (tcpd->rev->scps_capable) {
@@ -3313,6 +3310,7 @@ mptcp_add_analysis_subtree(packet_info *pinfo, tvbuff_t *tvb, proto_tree *parent
 
     proto_item_set_generated(item);
 
+#if 0 // nbOptionsChanged is currently unused.
     /* store the TCP Options related to MPTCP then we will avoid false DUP ACKs later */
     guint8 nbOptionsChanged = 0;
     if((tcpd->mptcp_analysis->mp_operations&(0x01))!=tcph->th_mptcp->mh_mpc) {
@@ -3348,6 +3346,7 @@ mptcp_add_analysis_subtree(packet_info *pinfo, tvbuff_t *tvb, proto_tree *parent
         nbOptionsChanged++;
     }
     /* we could track MPTCP option changes here, with nbOptionsChanged */
+#endif
 
     item = proto_tree_add_uint(tree, hf_mptcp_stream, tvb, 0, 0, mptcpd->stream);
     proto_item_set_generated(item);
diff --git a/epan/dissectors/packet-zbee-zcl-se.c b/epan/dissectors/packet-zbee-zcl-se.c
index ed852cd120..d91e862f36 100644
--- a/epan/dissectors/packet-zbee-zcl-se.c
+++ b/epan/dissectors/packet-zbee-zcl-se.c
@@ -11799,7 +11799,7 @@ dissect_zcl_calendar_publish_seasons(tvbuff_t *tvb, proto_tree *tree, guint *off
     proto_tree_add_item(tree, hf_zbee_zcl_calendar_total_number_of_commands, tvb, *offset, 1, ENC_NA);
     *offset += 1;
 
-    for (gint i = 0; tvb_reported_length_remaining(tvb, *offset) >= 5; i++) {
+    while (tvb_reported_length_remaining(tvb, *offset) >= 5) {
         /* Season Start Date */
         dissect_zcl_date(tvb, tree, offset, ett_zbee_zcl_calendar_season_start_date, "Season Start Date", hf_zbee_zcl_calendar_date_year, hf_zbee_zcl_calendar_date_month, hf_zbee_zcl_calendar_date_month_day, hf_zbee_zcl_calendar_date_week_day);