TCP: only store up to 1000 unacked segments (in each direction).

TCP: only store up to 1000 unacked segments (in each direction).

If we're seeing only one side of a conversation (we're not seeing any ACKs)
then things get really, really slow as the number of unacked segments grows.

1000 is, of course, an arbitrary limit.

Bug: 11589
Change-Id: I42652965b736da50122c722e6ac386c4d481e57f
Reviewed-on: https://code.wireshark.org/review/10971
Petri-Dish: Jeff Morriss <jeff.morriss.ws@gmail.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Anders Broman <a.broman58@gmail.com>