Do simple sequence analysis on ESP Sequence Number field

Change-Id: I84e204fb7a84eb821f4728a50945f34f4bdba73f
Reviewed-on: https://code.wireshark.org/review/4057
Petri-Dish: Michael Mann <mmann78@netscape.net>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Martin Mathieson <martin.r.mathieson@googlemail.com>