Change the way bans/purges are stored, so that each ban has a list of
conditions to test.

This paves the way for a much more expressive ban/purge syntax where
things like:

        purge req.http.host ~ "web1.com" && req.url ~ "\.png"
        purge obj.age > 1w && obj.size > 1MB
        purge obj.http.set-cookie ~ "USER=838339" && req.url ~ "\.html"

become possible.

Not quite there yet though.



git-svn-id: http://www.varnish-cache.org/svn/branches/2.0@3698 d4fa192b-c00b-0410-8231-f00ffab90ce4