mod_cache: Allow caching of requests with query arguments when Cache-Control

max-age is explicitly specified.

(Backport of r538807)

Reviewed by: jerenkrantz, fielding, rpluem


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@539280 13f79535-47bb-0310-9956-ffa450edef68