I haven't created the optional function to specify the cache_key yet,

I haven't created the optional function to specify the cache_key yet,
That will come after this patch.

ok.. brief summary of whats changed

* new Optional Directives
	* CacheMemEntrySize -- max size of a individual entry in memory
		cache
	* CacheIgnoreNoLastMod - so we can cache mod-included files

* it tries to figure out the size of the request based on buckets if the
	content-length header isn't set

* mem_cache now caches the subprocess_env & notes tables
* the CACHE_IN/OUT/CONDITIONAL run at FTYPE_CONTENT+1, so that
	all other content filters run BEFORE the cache in.

note: the code is still experimental, and we need a bit more work
mainly...
* garbage collection
* cache stats/reporting
* manual removal of a key.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@93030 13f79535-47bb-0310-9956-ffa450edef68