Switch the caching mutexes from reader/writer thread locks to global mutexes...

Switch the caching mutexes from reader/writer thread locks to global mutexes to allow for protection across processes rather than just across threads.

Reviewed by: bnicholes, minfrin, jjclar


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/APACHE_2_0_BRANCH@104493 13f79535-47bb-0310-9956-ffa450edef68