CHG: Refactor ffmpeg MT support
Merge pull request #5200 from koying/chgffmpegmt

CHG: Refactor ffmpeg MT support
[configure] Moved xbmc to SDL2
[depends] move to SDL2 for linux
[linux] Rewrite SDL_Joystick to use SDL2: adds hotplug support, correctly handles multiple joysticks and improves axis handling
[windows] WINJoystick: correctly handle multiple joystick and improve triggers
[buttontranslator] Add keymap attribute for axis-to-trigger mappings
[buttontranslator] Use regexes for joystick names in ButtonTranslator keymaps
[keymap] Add trigger attributes to 360 controller + altname for Razer Sabertooth
[keymap] Update PS3 keymap to use a regex name so it works OOB with sixad driver