MouseState.Button out of date

MonoGame stops processing mouse events when the game is not active, leading to the mouse buttons being 'out of date' when the game window becomes active again. 

Fix is to reset to current actual state on window activate.
> Are you saying that Control.MousePosition is in a different coordinate space 

Yes.

Mouse positions passed into the `MouseState` are relative to the window client area, meaning not including the title bar and window borders.

`Control.MousePosition` seems to be relative to the window area...  including the title bar and window borders.

If you fixed this then the position passed in when clicking on the title bar of a window would be something like 100, -8.   Don't think we should be passing that into the mouse state.

Anyway... we can discuss once I get into the office.