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;
            ^
```

5 files changed, 1 insertions, 15 deletions

diff --git a/ui/iface_lists.c b/ui/iface_lists.c
index 18f0b19bc8..dfeb0f7f9c 100644
--- a/ui/iface_lists.c
+++ b/ui/iface_lists.c
@@ -139,7 +139,6 @@ scan_local_interfaces_filtered(GList * allowed_types, void (*update_cb)(void))
     if_info_t         *if_info, temp;
     gchar             *descr;
     if_capabilities_t *caps=NULL;
-    gint              linktype_count;
     gboolean          monitor_mode;
     GSList            *curr_addr;
     int               ips = 0, i;
@@ -300,7 +299,6 @@ scan_local_interfaces_filtered(GList * allowed_types, void (*update_cb)(void))
         device.remote_opts.sampling_method = global_capture_opts.default_options.sampling_method;
         device.remote_opts.sampling_param  = global_capture_opts.default_options.sampling_param;
 #endif
-        linktype_count = 0;
         device.links = NULL;
         if (caps != NULL) {
 #if defined(HAVE_PCAP_CREATE)
@@ -321,7 +319,6 @@ scan_local_interfaces_filtered(GList * allowed_types, void (*update_cb)(void))
                     link->name = ws_strdup_printf("%s (not supported)", data_link_info->name);
                 }
                 device.links = g_list_append(device.links, link);
-                linktype_count++;
             }
 
             /*
diff --git a/ui/qt/io_graph_dialog.cpp b/ui/qt/io_graph_dialog.cpp
index 9c564c9aff..da8d94f38d 100644
--- a/ui/qt/io_graph_dialog.cpp
+++ b/ui/qt/io_graph_dialog.cpp
@@ -1929,7 +1929,7 @@ void IOGraph::clearAllData()
 void IOGraph::recalcGraphData(capture_file *cap_file, bool enable_scaling)
 {
     /* Moving average variables */
-    unsigned int mavg_in_average_count = 0, mavg_left = 0, mavg_right = 0;
+    unsigned int mavg_in_average_count = 0, mavg_left = 0;
     unsigned int mavg_to_remove = 0, mavg_to_add = 0;
     double mavg_cumulated = 0;
     QCPAxis *x_axis = nullptr;
@@ -1964,7 +1964,6 @@ void IOGraph::recalcGraphData(capture_file *cap_file, bool enable_scaling)
 
             mavg_cumulated += getItemValue((int)warmup_interval / interval_, cap_file);
             mavg_in_average_count++;
-            mavg_right++;
         }
         mavg_to_add = (unsigned int)warmup_interval;
     }
@@ -1989,8 +1988,6 @@ void IOGraph::recalcGraphData(capture_file *cap_file, bool enable_scaling)
                     mavg_in_average_count++;
                     mavg_cumulated += getItemValue((int)mavg_to_add / interval_, cap_file);
                     mavg_to_add += interval_;
-                } else {
-                    mavg_right--;
                 }
             }
             if (mavg_in_average_count > 0) {
diff --git a/ui/qt/models/profile_model.cpp b/ui/qt/models/profile_model.cpp
index 72ca4218ca..e300d2dd54 100644
--- a/ui/qt/models/profile_model.cpp
+++ b/ui/qt/models/profile_model.cpp
@@ -1139,7 +1139,6 @@ int ProfileModel::importProfilesFromDir(QString dirname, int * skippedCnt, bool
     {
         QFileInfoList entries = uniquePaths(filterProfilePath(dirname, QFileInfoList(), fromZip));
 
-        int entryCount = 0;
         foreach (QFileInfo fentry, entries)
         {
             if (fentry.fileName().length() <= 0)
@@ -1148,8 +1147,6 @@ int ProfileModel::importProfilesFromDir(QString dirname, int * skippedCnt, bool
             bool wasEmpty = true;
             bool success = false;
 
-            entryCount++;
-
             QString profilePath = profileDir.absolutePath() + "/" + fentry.fileName();
             QString tempPath = fentry.absoluteFilePath();
 
diff --git a/ui/qt/stats_tree_dialog.cpp b/ui/qt/stats_tree_dialog.cpp
index 8492e8e57d..1ec66b7e1f 100644
--- a/ui/qt/stats_tree_dialog.cpp
+++ b/ui/qt/stats_tree_dialog.cpp
@@ -163,7 +163,6 @@ void StatsTreeDialog::drawTreeItems(void *st_ptr)
     if (!st || !st->cfg || !st->cfg->pr || !st->cfg->pr->st_dlg) return;
     TapParameterDialog *st_dlg = st->cfg->pr->st_dlg;
     QTreeWidgetItemIterator iter(st_dlg->statsTreeWidget());
-    int node_count = 0;
 
     while (*iter) {
         stat_node *node = VariantPointer<stat_node>::asPtr((*iter)->data(item_col_, Qt::UserRole));
@@ -177,7 +176,6 @@ void StatsTreeDialog::drawTreeItems(void *st_ptr)
                                  (!(node->st_flags&ST_FLG_DEF_NOEXPAND)));
             g_free(valstrs);
         }
-        node_count++;
         ++iter;
     }
 
diff --git a/ui/voip_calls.c b/ui/voip_calls.c
index c22edd6d6b..62576ddab0 100644
--- a/ui/voip_calls.c
+++ b/ui/voip_calls.c
@@ -453,7 +453,6 @@ static void insert_to_graph_t38(voip_calls_tapinfo_t *tapinfo, packet_info *pinf
 {
     seq_analysis_item_t *gai, *new_gai;
     GList    *list;
-    guint     item_num;
     gboolean  inserted;
     gchar     time_str[COL_MAX_LEN];
 
@@ -484,7 +483,6 @@ static void insert_to_graph_t38(voip_calls_tapinfo_t *tapinfo, packet_info *pinf
     new_gai->time_str = g_strdup(time_str);
     new_gai->display=FALSE;
 
-    item_num = 0;
     inserted = FALSE;
 
     list = g_queue_peek_nth_link(tapinfo->graph_analysis->items, 0);
@@ -498,7 +496,6 @@ static void insert_to_graph_t38(voip_calls_tapinfo_t *tapinfo, packet_info *pinf
             break;
         }
         list = g_list_next(list);
-        item_num++;
     }
 
     if (!inserted) {