winemac: Use NSMouseInRect() instead of NSPointInRect() to compensate for Cocoa's off-by-one coordinate system.

This matches what Cocoa does when determining how to handle an event so that,
for example, our test if a click is in the window grow box corresponds to
whether Cocoa will run an internal mouse-tracking loop to resize the window
when we pass it the event.  This fixes a problem where both Cocoa and user32
would try to run a resize loop and the cursor would get "stuck" resizing the
window after the button was released.