Add a backend property ".host_header" to set default content of Host:
header if client didn't provide one.

If .host_header is not specified, it defaults to .host.

Add testcase for this logic.

(Incidental change: Use "interval" instead of "rate" for backend pollers.)





git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@2938 d4fa192b-c00b-0410-8231-f00ffab90ce4