First cut at mod_disk_cache, based on code from the IBM AS400 team. Still

      need to cleanup where some bytes are stored, check-in routines this module
calls in cache_util, etc.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@93193 13f79535-47bb-0310-9956-ffa450edef68