Adding --with-auth_request as a flag

Uses the --with-http_auth_request_module flag of the 1.5.x configure script.
Since it's only working on 1.5, I added a test for the devel version which is
currently at 1.5.6 in contrast to stable which is at 1.4.3.

The current formula only contains the most basic flags, and I am totally not sure if this patch is appropriate, but i had it lying around and figured it might be useful while not actually breaking anything so I wanted to at least try to get it merged. Discard/close at will!

Thanks,

Jan