Bump d3d12.h to the version from vkd3d-proton

I realise that this might be slightly inappropriate given that the name of this repo suggests that it's a straight extraction of the mingw headers.

This is however very handy to have alongside dxvk's native windows headers

Worth mentioning that vkd3d-proton is also lgpl 2.1 licensed.

FWIW, this would only be useful for me if it were also included eventually in dxvk, @doitsujin, would this be possible?

To do it totally officially is a really onerous task:

• submit patch to wine and wait for it to be merged
• submit patch to mingw updating their headers from the latest wine version and wait for it to be merged
• make PR here with that update
• make PR to dxvk updating the submodule for this repo
• make PR to nixpkgs bumping dxvk to get the headers on my system

While it's certainly not impossible for me to package and distribute the up to date headers I'd like myself, it's definitely a long term ease to have them packaged properly with dxvk (similarly rationale behind https://github.com/doitsujin/dxvk/pull/3361)

I am not sure this is the right approach. The DX12 headers get updated frequently and also vkd3d-proton which uses IDL to generate the header uses this project.

DXVK shouldn't package or provide these headers, installing vkd3d-proton should.

The issue I've bumped into is that mixing and matching the d3d12 header from vkd3d-proton with the dxgi header from dxvk is just not really possible. They both end up redeclaring some of the same things or including their windows.h alternatives, if there's a neat way of using both then I'm all ears. I definitely agree in principle however/

I had a go at modifying the dxgi header in dxvk to be compatible with the d3d12 header from vkd3d-proton, but it's very hard to untangle from the rest of the header machinery in dxvk. Compared to this (mostly) mechanical change it's a lot of work!