Introducing $MCACHE - Memory-based cache

Introducing $MCACHE - Memory-based cache

$MCACHE is initially based on core API that is shared between memcached and
turckmmcache/eaccelerator. The core operations are add(), set() and delete()

This initial implementation uses the PECL-based PHP client. Would be trivial
to add support for a PHP-based client.

The $MCACHE facility can be used for DB cache, text filters cache, and possibly
for sessions.