The cache_hash, cache_pqueue and cache_cache functions

The cache_hash, cache_pqueue and cache_cache functions
are undecorated, their .h files are not propagated into
an installed include/ tree, and were erroniously exported.

This doesn't require an mmn bump, because anyone who might
have consumed these modules would have succeeded only with
win32, consuming private headers, and absolutely fails on unix.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@664149 13f79535-47bb-0310-9956-ffa450edef68