generatemouseevent API reworked by Opera team

Copyright (C) 2013 Opera Software ASA.  All rights reserved.
This file is an original work developed by Opera Software ASA

"""This file contains an override for atomac.ldtp's generatemouseevent.

The Mac implementation lacks several types, these are implemented here,
along with the those that are already supported, so this library can
function as a drop-in replacement."""

Thanks Sigbjørn Vik <sigbjorn@opera.com> for their contribution