Associate ascii representation addr/port strings with each listen
socket, already in the manager process.

Postpone listen(2) call until client is ready, to limit initial 
connection spike.

XXX: I still miss an unlisten(2).



git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@2658 d4fa192b-c00b-0410-8231-f00ffab90ce4