(Varnish Stream Sockets) as I intend to eventually add support for AF_UNIX
sockets.

This also moves the accept filter code out from VSS_listen() (previously
TCP_open()) and into a separate function in tcp.c


git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@1500 d4fa192b-c00b-0410-8231-f00ffab90ce4