Merge r239406 with the 2.2.x branch. Again, no functional changes; this rev

moves some structures and define's shared by mod_disk_cache and htcacheclean
into a single mod_disk_cache.h.  

Original Author: asteinmetz
Review by: colm


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@292557 13f79535-47bb-0310-9956-ffa450edef68