Merge a bunch of changes to TCP compressed TIME_WAIT state handling

Merge a bunch of changes to TCP compressed TIME_WAIT state handling
that was done by myself and ru@ in HEAD:

o Remove a code from in in_pcblookup_local() that can lead to
  million times looping in this function.
o Rewrite the storage of tcptw entries to simple TAILQ. The
  more complex double LIST is not needed anymore since T/TCP
  is removed.
o Add possibility to change net.inet.tcp.maxtcptw via sysctl
  and load time tunable. Do not modify maxtcptw if it was set
  explicitly, if maxsockets is modified.
o Add sysctl that allows to suppress creating time wait states
  for sockets, where both endpoints are local.

Approved by:	re (kensmith)