initial port of new Request-mode HTTP_IN filter to proxy.

Status: It serves a reverse-proxy page.. but SLOWLY.
VERY SLOWLY.
still looking at why, but now it serves pages instead of dumping core.
PR:
Obtained from:
Submitted by:
Reviewed by:


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@91363 13f79535-47bb-0310-9956-ffa450edef68