[Feature Request] Add support for X11 WSI

[bkaradzic]

This is not issue, rather feature request... Sorry! 😃

It would be great if DXVK can be used directly with X11 without SDL.

I already did some work, it's not complete, but it works enough for my use case (using D3D11 for testing on Linux directly without SDL):
bkaradzic@38b5f66

[flibitijibibo]

It might make things easier to rebase on #3738, which allows all the backends to live in one binary.

[doitsujin]

#3738 is definitely going to happen first, but I'm not opposed to having an X11 backend added afterwards.

Is the xlib path relevant? Given that the headers are such a huge pain in the arse to work with and have #defines for literally every English word in existence, I'd strongly prefer to not have to deal with it and just have an xcb path.

[flibitijibibo]

The WSI changes got merged, so it should now be possible to add xcb/xlib support in the same binary as SDL/GLFW.