2 specific changes to USBDriver module
John Ballance authored
        Added (and fixed code underlying) to give periodic
        explore of USB busses (cf NetBSD).
        Added USBDisover command to let user provoke this too.
        Reworked USB device number allocation to roll
        around at 999 to avoid field overflow in
        a number of places.
Detail:
Admin:  castle added IP. to be beta tested on beta test site


Version 0.37. Tagged as 'NetBSD-0_37'
6a08f2c6