[AD] OSX and Windowed mouse behaviour

[Charles Wardlaw <kattkieru@xxxxxxxxxx>]

Hi all,

I've noticed that under OSX in windowed mode, the system mouse pointer
and the Allegro mouse pointer sometimes become unsynced.  I was looking
in src/macosx/system.m, in the window handler code, and noticed that
the code only seems to track mouse deltas, which would explain this
behaviour -- might it be better in windowed mode to check the mouse
position by doing NSPointInRect(mousecoords, view), and then warping
the mouse pointer to this new point?

- Charles