These are declared CACHE_DECLARE and should be consumed

These are declared CACHE_DECLARE and should be consumed
from mod_cache by mod_mem_cache.  The duplicate cache_util
import is a dead giveaway that this was broken.

In order to backport, an MMN bump would be required because
these cache_pqueue, cache_cache and cache_hash exported
functions would be added to the "contract" of functions
which are available from mod_cache for third party cache
providers.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@664136 13f79535-47bb-0310-9956-ffa450edef68