Add a reference to the first backend {} we encounter, it is the default.
Add a reference to all backends assigned explicitly.
Add a reference to all methods.

Enable reference check, complain if: backend, function or acl is defined
but not used, or used but not defined.



git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@227 d4fa192b-c00b-0410-8231-f00ffab90ce4