libs: EOL fun of SDL2

libs/SDL2/docs/README-android.md

libs/SDL2/docs/README-cmake.md

libs/SDL2/docs/README-directfb.md

libs/SDL2/docs/README-dynapi.md

libs/SDL2/docs/README-emscripten.md

libs/SDL2/docs/README-gesture.md

libs/SDL2/docs/README-hg.md

libs/SDL2/docs/README-ios.md

libs/SDL2/docs/README-linux.md

libs/SDL2/docs/README-macosx.md

libs/SDL2/docs/README-nacl.md

libs/SDL2/docs/README-pandora.md

libs/SDL2/docs/README-platforms.md

libs/SDL2/docs/README-porting.md

libs/SDL2/docs/README-psp.md

libs/SDL2/docs/README-raspberrypi.md

libs/SDL2/docs/README-touch.md

libs/SDL2/docs/README-wince.md

libs/SDL2/docs/README-winrt.md

libs/SDL2/docs/README.md