Eventually we should get rid of separate allocations on every
TryGetFontTable(), that's not how local loader works. Instead it maps
font file and returns pointers to a mapping, context is always NULL in
this case.

We don't support p8 color keying either way.

Using glGammaInternal or rtInternal should do the right thing in principle,
although in practice they should never get used either way.

NSBezierPath doesn't override the -isEqual: method to actually compare paths,
so it just falls back to object identity which, in our case, makes paths seem
like they're never equal.

Also, memcmp()-ing the rectangle array is almost certainly faster than any
general test for equality between two paths.

winemac: Don't invalidate the window shadow on every draw if it's merely shaped and not color-keyed or using per-pixel alpha.

This avoids flickering and tearing on some versions of OS X during frequent
redrawing in a shaped window, such as when scrolling a document in Word 2007.

Since we aren't guaranteed that the window surface has updated bits for us to
draw, we mark the whole content view as needing redisplay and draw the window's
shape in the background color on the first -drawRect: after the shape change.