Build memcached with cmake

Change-Id: I1d2809ff8c0c8440a6ed79a1f8915880af3acf09
Reviewed-on: http://review.couchbase.org/28753
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>