Add proxy Via: header management. Currently, Via: headers can be left

unchanged (compatibility), can be set to protocol and host only,
or to protocol, host and comment. Optionally, all Via: headers can
be suppressed if intranet privacy in companies is desired when going out
over a firewall apache.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@81939 13f79535-47bb-0310-9956-ffa450edef68