Apache 1.3 patch for ProxyPreserveHost

Patch against Apache 1.3.41 ((Yep, still running 1.3 around the place)) to backport the ProxyPreserveHost feature. I can't remember where I found it now, but I've tweaked it through a few Apache revisions.

Useful for migrating sites from one host to another before or during DNS propagation.

That said, I'm using Varnish and HAProxy an increasing amount for such plumbing.