Splitted off cache defines/structs used by htcacheclean.

This makes htcacheclean again independent from httpd.h.
Submitted by: NormW <normw gknw net>


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1033779 13f79535-47bb-0310-9956-ffa450edef68