Create the possiblity for the the acceptor to send the session directly

Create the possiblity for the the acceptor to send the session directly
to the workerpool instead of taking the detour around the session-herder.

This saves a context switch and is presumabley a good idea because the
majority of sessions will have requst already in the pipeline.

For accept filters it makes even more sense because we know this to
be the case.

git-svn-id: svn+ssh://projects.linpro.no/svn/varnish/trunk@866 d4fa192b-c00b-0410-8231-f00ffab90ce4