Cleanup patches

[Christian Fetzer]

Currently we have these patches applied to libretro cores:

• vfs patches in scummvm, genplus and blumsx (they should stay for the moment)

These patches should be checked if they are still needed (and are still applying) and if they can be sent upstream:

• all done

Done:

• cross compile patches in snes9x2010, bsnes-mercury (dropped as we don't use them)
• dosbox - 0001-Fix-infinite-loop-on-exit.patch Pending PR libretro/dosbox-libretro#47
• mupen64plus - 01-use-c-buttons-without-modifier-key.patch Rebased, clarified with @a1rwulf that they are only for local testing
• mupen64plus - 02-remove-specialization-of-controller-map.patch Rebased, clarified with @a1rwulf that they are only for local testing
• pcem - 01-inline.patch libretro/libretro-pcem#2
• pcem - 02-settings.patch libretro/libretro-pcem#2
• snes9x2002 - 0001-Fix-compilation.patch Dropped, not needed.
• pcsx_rearmed - 0001-Remove-configure-file.patch unneeded
• pcsx_rearmed - 0001-aarch64-support.patch unneeded (LE specifc)
• prboom - 00-no_vfs.patch kodi-game/game.libretro.prboom#1