This fixes a problem where the underlying cache code

This fixes a problem where the underlying cache code
indicated that there was one more element on the cache
than there actually was. This happened since element 0
exists but is not used. This code allocates the correct
number of useable elements and reports the number of
actually used elements. The previous code only allowed
MCacheMaxObjectCount-1 objects to be stored in the
cache. [Paul J. Reder]

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@97510 13f79535-47bb-0310-9956-ffa450edef68