Remove compile warnings on MacOSX with htonll

Change-Id: I33e1ca3992a6c1eebbe8ea970b0d6dcc174b1ead
Reviewed-on: http://review.couchbase.org/42835
Reviewed-by: Dave Rigby <daver@couchbase.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>