Backpedal a bit.

Jamie noticed that my last fix was flawed because the anti aliasing setting isn't part of the
graphics context, so save/restore state isn't enough to handle it. Then I did more digging and
noticed that the interpolation fix doesn't require the anti-aliasing tweak, and the interpolation
setting doesn't affect the smoothness of rendered text, so we end up with something much simpler
in the end.