There are still some issues on Windows, especially with Dual Shock controllers, but a larger rewrite is required anyway of the input handling so it's not worthwhile trying to fix it at this time.
This resolves an irritating issue in the code editor where SDL2-specific functions could't be found. Not entirely sure about the SDL include file logic for other operating systems than Linux so the #ifdef directives may need to be updated further at a later date.
* add hotkey button gfx and hotkey to input configuration
* prompt user if no hotkey set, and offer to use select
* if no hotkey is set, still save an entry with key id 0, for backward compatibility