Add CHANGES entry in mod_mem_cache patch relating to PR 45049.

While at it, propose another fix for mod_mem_cache relating to PR 43724.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@1750730 13f79535-47bb-0310-9956-ffa450edef68