*) Fix segfault in mod_mem_cache cache_insert() due to cache size
   becoming negative.  PR: 21285, 21287

  Submitted by: Bill Stoddard, Massimo Torquati, Jean-Jacques Clar
  Reviewed by: stoddard, rederpj, trawick


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/APACHE_2_0_BRANCH@102489 13f79535-47bb-0310-9956-ffa450edef68