(SDL) Fix #ifdef typo

Signed-off-by: Higor Eurípedes <heuripedes@gmail.com>
(SDL) Fix double initialization

Signed-off-by: Higor Eurípedes <heuripedes@gmail.com>
(scaler.c) Add missing RGBA4444 to ARGB8888 conversion

Signed-off-by: Higor Eurípedes <heuripedes@gmail.com>
(SDL2) Use SDL_INIT_GAMECONTROLLER

Signed-off-by: Higor Eurípedes <heuripedes@gmail.com>
(SDL2) Add SDL Game Controller (xinput and friends) support

Signed-off-by: Higor Eurípedes <heuripedes@gmail.com>
(SDL*) Add joypad auto configuration support
(SDL2) Show available video drivers and fix typo
(SDL2) Remove double header inclusion
Merge pull request #889 from heuripedes/sdl2-improvements

SDL2 improvements