XCode 6 contains ntohll

Change-Id: I59723cd17b36b472e9c3f03169d581cb7b1fe4c3
Reviewed-on: http://review.couchbase.org/42300
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: buildbot <build@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>