New mod_proxy/mod_cache (file cache) for 2.0. This uses a caching API so

that shared mem, LDAP servers, DBs, etc. can also be used for proxy
caching. The caching API is very young, and subject to change as APR changes.

proxy_cache.c from the proxy subdir is no longer used.

Build with --enable-modules=proxy,cache

Lightly tested on Linux, no warranties expressed or implied yet.

Still to do:

strerror(), waitpid(), stat() cleanups
address issues marked by @@@FIXME
add HTTP/1.1

This should be considered a *reference* proxy implementation for 2.0. What
actually ends up shipping with 2.0 is likely going to be rather different as
the redesign evolves. This may end up being the 2.0 backwards compatibility
workalike.

Modified to work with today's conf/build/layout scheme

PR:
Obtained from:
Submitted by:	Sam Magnuson
Reviewed by:	Chuck Murcko


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@85552 13f79535-47bb-0310-9956-ffa450edef68