and create a function to figure this out, if present.

Add the req.hash variable and the += operator for it, so we
can put the actual hash contents under vcl control.

The runtime half of this stuff is not done yet.



git-svn-id: http://www.varnish-cache.org/svn/trunk@1395 d4fa192b-c00b-0410-8231-f00ffab90ce4