Support creating D3D9 device without a window

[K0bin]

In spite of what the documentation says, it's possible to create a D3D9 device with NULL passed for both PresentationParams::hDeviceWindow and FocusWindow. This will still create an implicit swapchain and you can query the backbuffers and render to those. You can even call Present and that returns S_OK.

According to Wine commit logs, Planetary Annihilation: Titans depends on this. This also makes the "visuals" Wine test crash with DXVK.

[misyltoad]

I seem to remember this not working for me which is why the DXVK tests all have windows.

[K0bin]