added serial mouse driver for Microsoft and Mousesystems mice
* Both drivers use the interface defined in serial_mouse.h
* They should work with any UART implementation (hardware/software UART)
* The Microsoft driver is currently untested.
The Mousesystems driver is confirmed to work.
- the 100ms delay causes keystroke drop; this is observable with
pressing Numlock key on AEK repeatedly
- without the delay LED sync problem doesn't occur now
Robin Haberkorn
tmk