Region selection is broken on systems with multiple monitors

[robindegen]

The screen gets squashed to the left (black bar on the right) and the selection doesn't work at all, probably due to mouse cursor positions not being correct.

[stevenhoving]

Region selection is broken on system who have swapped the main display.

part 2: the getcursorpos handles multiple monitors in a weird way: \see https://social.msdn.microsoft.com/Forums/vstudio/en-US/34bd062d-2100-4925-bdfa-9f98b881e7dc/winapi-getcursorpos-returning-incorrect-pointers-with-multiple-monitors?forum=vcgeneral

• [ ] convert rectangle selection code to use normalized values.

[stevenhoving]

fixed