Move the VRT initializer for simple backends home.

Add a backend method to get hostname.  This may be a hack.

Move fields private to "simple" to its private structure.

Add cleanup method to backend, so we can collect the garbage.



git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@1895 d4fa192b-c00b-0410-8231-f00ffab90ce4