2 updates to the Logitech MX5000 key mappings:
1. Fix Logitech MX5000 Media key mapping:
The MX5000 has a key clearly marked "media" (in text) and when they gets
pressed the keyboards LCD briefly shows "MEDIA" in a big font.
Yet the keyboard sends a HID usage code which according to the HUTT
is config/control-panel. Map this to media so that the key behaves as
labeled.
2. Add mapping for the scan-code send by the Fn on/off toggle key
