This is simpler and is also more robust. The display no longer needs to
know whether it is fullscreen or not when reporting the size.

This should fix bugs whereby leaving fullscreen forces the window to be
maximized. On the other hand, it will fail if the windowing system
automatically resize a fullscreen window (due to changing view port).

This enables recycling the window when multiple window types are
involved. and avoids visual glitches.

All window manager override the parameters anyway. This never worked.

(same priority as XCB embedded window)

This is so that a window of "any" type can be requested rather than
only a window of a specific type.