USB Gamepad support

USB gamepad controllers connected to the RPi's USB ports can be used to control Commodore games or applications. There is a revised joys tool, run from the idun-shell, to configure a controller. Then, the buttons are mapped and can be utilized on the C128 in either native programs or programs that use the idun kernel.

As a proof-of-concept, a modified version of Galaga (galaga-usb) and a modified "shareware" version of PETSCII Robots 128 (Robots-128.d71) are now included in the idun-base/games repository.