libmemcached is renamed to libmcd

Change-Id: I264263f43b0a26fa27b399444f8b6c5435c86241
Reviewed-on: http://review.couchbase.org/30170
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>