TLS: Implement reassembly for Handshake messages

Lack of handshake reassembly caused Certificate handshake messages to be
reported as "Encrypted Handshake Messages" and broke decryption in some
cases. Fix this by properly tracking handshake fragments and delay
dissection until all fragments are available.

Now when a fragmented Handshake message is found:

* The first fragment will have "(fragmented)" appended to the record
  tree item as well as the "Handshake Protocol" item.
* "Reassembled Handshake Message in frame: X" is added for fragments.
* The last reassembled handshake message will be displayed together with
  a fragment list.

Note: Previously, handshake records with a message length larger than
the available data was assumed to be encrypted. This restriction had to
be lifted, but can now cause false positives (reporting encrypted data
as unencrypted handshake fragments).

The provided capture is not minimal but should be comprehensive as it is
generated with randomly sized TLS record and TCP segment lengths using
`./tls-handshake-fragments.py hs-frag.pcap --seed=1337 --count=100` and
https://git.lekensteyn.nl/peter/wireshark-notes/tree/crafted-pkt/tls-handshake-fragments.py
(A copy of this script is attached to bug 3303.)

Bug: 3303
Bug: 15537
Bug: 15625
Change-Id: I779925aba30548a76c20e0e37b39d01d2c88a764
Reviewed-on: https://code.wireshark.org/review/32857
Petri-Dish: Peter Wu <peter@lekensteyn.nl>
Tested-by: Petri Dish Buildbot
Reviewed-by: Alexis La Goutte <alexis.lagoutte@gmail.com>
Reviewed-by: Peter Wu <peter@lekensteyn.nl>

1 files changed, 0 insertions, 0 deletions

diff --git a/test/captures/tls-fragmented-handshakes.pcap.gz b/test/captures/tls-fragmented-handshakes.pcap.gz
new file mode 100644
index 0000000000..9f97664ddf
--- /dev/null
+++ b/test/captures/tls-fragmented-handshakes.pcap.gz