Revert prior commit; the flaw is not in exporting all

of these cache_* functions, but in declaring them 
exported in the first place.  _hash, _pqueue and cache_cache
are undecorated and were erroniously exported.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@664142 13f79535-47bb-0310-9956-ffa450edef68