For now all we have is a "simple" method, but we want more complex
methods later on, round-robin, least-busy and so on.

For now, fall into the other ditch and move everything to 
cache_backend_simple.c, we will move bits back as the gain generality.



git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@1892 d4fa192b-c00b-0410-8231-f00ffab90ce4