Major rewrite of the VSL handler for increased robustness and clarity:

Major rewrite of the VSL handler for increased robustness and clarity:

 - Treat all request fields in a similar manner.

 - Mostly eliminate fixed-size buffers.

 - Don't print or format anything until we see ReqEnd.

 - If we saw a Host: header, use it to generate an absolute URI,
   resulting in far more useful output when processing logs from a
   server which handles multiple virtual hosts.

git-svn-id: svn+ssh://projects.linpro.no/svn/varnish/trunk@1362 d4fa192b-c00b-0410-8231-f00ffab90ce4