Allow Server response headers to be logged via the proxy.

PR: #7461
Submitted by: patrik@netdive.com
Reviewed by: Victor Orlikowski


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@89323 13f79535-47bb-0310-9956-ffa450edef68