Fixing the mod_proxy docs. The docs were transferred away without a history,

Fixing the mod_proxy docs. The docs were transferred away without a history,
so I'm applying each of the new patches one by one (there are only a few of
them) so that the new mod_proxy.html file is up to date.
This first patch returns the original doc to the tree. Subsequent patches
will apply the changes to the file up to date.
PR:
Obtained from:
Submitted by:
Reviewed by:

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@91195 13f79535-47bb-0310-9956-ffa450edef68