Add in mod_cache.c r1.91 to the backport of the mod_cache Expires fix.

 (Technically, it invalidates FirstBill's vote; but I'll let it slide...)

Also propose the mod_disk_cache race condition fix.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/APACHE_2_0_BRANCH@105269 13f79535-47bb-0310-9956-ffa450edef68