Capture / Record screenshots using DirectX

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This is based on: https://github.com/spazzarama/Direct3DHook

I ran into some issues with the original code (fullscreen alt-tabbing, lost devices, etc.)

I studied and ported the Direct3D hook from the OBS project (https://github.com/jp9000/OBS)

Note that this OBS hook is overkill for taking screenshots. It records a constant stream, and uses buffers to optimize it. Way too much for just taking some screenshots.

After porting it, studying it and reading some Direct3D documentation. I got a better understanding of how to implement the original screenshot hook.

NOTE: The original hook I ported from OBS is called DXHookD3D9Obs. It still has bugs, because I didn't continue testing it.

NOTE2: OBS is licensed under GPL (see COPYING). As this project now contains work originally created by OBS authors, it's licensed as GPL as well.