Add option to disable joystick input

Fixes #6082 (according to @kevingranade the reason for that bug is the joystick driver).

The default for this option is to enable the joystick.
I'm not sure if it's safe to call SDL_JoystickOpen(0); if SDL_NumJoysticks(); returns 0, which can happen now.
Maybe move SDL_NumJoysticks(); outside the conditional again, and have the conditional be:
if( OPTIONS["ENABLE_JOYSTICK"] && numjoy >= 1 ) {