new: TCP now synchronize one direction with regard to the other

Before, TCP streams were reordered in both directions individually, which
confused some parsers (for instance, HTTP parser may see an answer before
the query. Now, TCP uses the acknowledgment number to put on hold segments
that ack something we have not received yet.

Of course if your junkie is in bridge this problem never hit you, but when
the traffic is mirrored to your junkie that's another story.
chg: better progressive timeout of pkt_wait_lists

Simpler as well...
chg: graceful parsing of remaining packets at the end

Now that we know how to signal gaps we can send everything that's left
on a pkt_wait_list to the parser when we get rid of it.
fix: since we pass NULL packets (for gaps) we should be able to restart NULL.
Merge branch 'tcp-synch'