explicit usage of ctypes namespace

there is no need to populate namespace with something that you
don't use. It can only introduce more unexpected bugs.

explicit "ctypes." namespace prefix makes code more readable and
safe.

Change-Id: I0abf234cf3061cdd4538ac5b7fa46e8724e67eda
Reviewed-on: http://review.couchbase.org/34108
Reviewed-by: Aaron Miller <apage43@ninjawhale.com>
Tested-by: Aaron Miller <apage43@ninjawhale.com>