SDL_VideoCapture: use 0-copy for backend android and linux/v4l2

[1bsyl]

this allows to do 0-copy when doing video capture.

linux (x11) / android back-end.

I re-applied the patch I wrote before. This used to work with android and linux. currently:

• not re-tested on Android.
• working on linux / x11. But width/height/pitch are probably wrong

to try: compiles "testvideocaptureminimal.c" with USE_DMABUF set to 1

[slouken]

Just a note for future us, I'm thinking that we add a way to request a zero copy texture as properties rather than a surface. That way we can support GPU textures on DXGI, Vulkan, etc.