Enable sdl_gl for SDL2 windows builds
Merge pull request #894 from heuripedes/master

Enable sdl_gl for SDL2 windows builds
(PSP1) Fix build
(settings) Set autoconfig_dir if g_defaults.autoconfig_dir is set
(sdl_gl) Fix segfault
Allow SDL2 drivers to be used as default drivers
(sdl_gl) Merge SDL and SDL2 event loops
(SDL) Use SDL_PeepEvents instead of SDL_PollEvent
Merge pull request #896 from heuripedes/master

SDL fixes
(Menu) Refactor ST_UINT labels
(Menu) Refactor Netplay TCP/UDP Port setting
(Menu) Refactor autosave_interval setting
(Menu) Refactor more ST_FLOAT code
(Menu) Change rounding fraction to snprintf format
(Menu) Change rounding_fraction to const char*
(Settings/Menu) Refactor video_refresh_rate_auto
(Menu) Move up setting 'video_smooth'
(Menu) Refactor VIDEO_MONITOR_INDEX setting
(Menu) Refactor ST_DIR settings
(GL) Fix build in case HAVE_FBO is not defined