Merge branch 'master' into next

appveyor.yml

libs/SDL2/BUGS.txt

libs/SDL2/COPYING.txt

libs/SDL2/CREDITS.txt

libs/SDL2/INSTALL.txt

libs/SDL2/Makefile

libs/SDL2/README-SDL.txt

libs/SDL2/README.txt

libs/SDL2/WhatsNew.txt

libs/SDL2/docs/README-android.md

libs/SDL2/docs/README-cmake.md

libs/SDL2/docs/README-directfb.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-pandora.md

libs/SDL2/docs/README-porting.md