Implementation of X11 cursor handling using NSCursor instead of QuickDraw CCursHandle.
Replaces hw/darwin/bundle/quartzCursor.c. hw/darwin/bundle/Imakefile also needs to be updated to refer to the .m instead of the .c.
Tested with fvwm2's window sizing cursors (various sizes). NOT tested with a real color cursor. NOT tested with cursors larger than 16x16. MallocDebug finds no obvious errors.