* Setting the same mouse cursor twice is a no-op
* Cocoa: Call [NSCursor set] to change mouse cursor
The previous way, changing the mouse cursor was handled by invalidating
the mouse cursor rectangles and then recreating them (with the new
cursor) the next event loop. This is extremely slow; sometimes it can
take over a millisecond! With [NSCursor set] it happens instantly and
very quick performance-wise.
The downside is that it sets the cursor for the whole screen, so we
have some guards in place to change it to the system cursor if
the mouse moves outside the window or the window loses focus.
* Cocoa: Remove unneeded resetCursorRects: function
Sean Ridenour