Swap joystick ports 0 and 1 (mode and device) with shortcut Mod+J

[FrodeSolheim]

Useful if playing a two-player (not simultaneous game) which uses two joysticks for input, and you want to quickly toggle which of the Amiga joysticks you control with a single host joystick.

Bonus feature: Maybe this can be toggled with a button combination on the controller itself (e.g. SELECT+something).