DDraw can draw to the front buffer only, thus there's never a Present
call which could pass this window. Due to that a drawing-independent
method is needed.
This is a long-needed cleanup aimed at removing the ddraw_primary,
ddraw_window, ddraw_width and ddraw_height members from
IWineD3DDeviceImpl, which just do not belong there. Destination
window and screen handling is supposed to be done by swapchains.
