High-level GameController bindings

[ramirez7]

There are bindings for events, but in order to actually use the GameController interface & use those events, you must dip down into SDL.Raw:

• You have to use SDL.Raw.gameControllerAddMappingsFromFile et al to load a mapping file.
• You have to use SDL.Raw.gameControllerOpen to initialize the controller(s) so that events come through.
• controllerAxisEventAxis is just an untyped Word8 despite being a C enum.
  • There are bindings in SDL.Raw to the enum, but they are the wrong type (Word32).
• There are also lots of useful functions not bound (such as the ones to get the current state).