Improve compatibility with RetroArch/Libretro

[nefarius]

Doing a bit of testing with RetroArch I noticed rumble support and button mapping isn't as straight forward as expected.

Apparently only sdl2 and xinput support vibration. XInput introduces an additional layer of emulation that can be avoided, so since dinput and therefore FFB is apparently not supported (anymore?) we'd need to take a look at the sdl2 driver.

First tests with sdl2 were not successful; mapping is all over the place and I couldn't yet get rumble to work.

Keeping this issue as a reminder for doing more testing and maybe adjust the modes.

See Libretro Docs.