Backport:

   * mod_cache: Let Cache-Control max-age set the expiration date. 
        Trunk version of patch:
         http://svn.apache.org/viewvc?view=rev&revision=539063
        2.2.x version of patch:
         http://people.apache.org/~jerenkrantz/max-age-expire-2.2.x.patch
         (No ->minex in 2.2.x)
        +1: jerenkrantz, fielding, striker



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@539430 13f79535-47bb-0310-9956-ffa450edef68