gdkwindow-quartz.c patches

richard, i've posted a snapshot of my work-in-progress to properly map between X11 and Quartz drawing semantics. its not finished, in the sense that i still have a significant issue to fix (once i discover what it is), but it does provide *much* better drawing response than the code in svn right now.

the patch can be found at http://ardour.org/files/gdk2.patch

there is still a very basic problem with drawing speed in gdk-quartz. i will try to come up with a simple demo case in the next 48hrs or so.