ssl-utils: dissect the certificate type TLS extension

This analyses the certificate type extensions and then stores the
certificate type in the ssl session. This way we can later show the
certificate in the correct from.

This is described in this draft:
https://tools.ietf.org/html/draft-ietf-tls-oob-pubkey-11

Change-Id: Ifdda165807bc29f1fc138da000a9a538ecd18b6e
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Reviewed-on: https://code.wireshark.org/review/1371
Reviewed-by: Alexis La Goutte <alexis.lagoutte@gmail.com>
(cherry picked from commit 584b81372b70f3fbb28e35df145215778b0d6663)
Reviewed-on: https://code.wireshark.org/review/2815
Reviewed-by: Anders Broman <a.broman58@gmail.com>