[Examples] Added PointToClient test
[Platform] More selective mouse events

We should not raise mouse events when the cursor state hasn’t changed.
[Platform] Forward PointToScreen to backend
[Mac] Fixed PointTo* calculations

On HiDPI displays, the client rectangle is using a pixel-based
coordinate system, while the screen is using a point-based coordinate
system. PointToClient/PointToScreen now correctly accounts for that.
[Examples] Test MouseCursor in GameWindowStates