Squash libmemcached into moxi

We're using our own fork of an old version of libmemcached
in moxi and that's the only client we have using libmemcached.
Squashing the repository into moxi makes it easier to build
the product.

Change-Id: I783326fb75bfe2b1487ef4a94704a77428e9ad8d
Reviewed-on: http://review.couchbase.org/34782
Reviewed-by: Chris Hillery <ceej@couchbase.com>
Tested-by: Chris Hillery <ceej@couchbase.com>