INT 16 - KEYBOARD - SET TYPEMATIC RATE AND DELAY
        AH = 03h
        AL = subfunction
            00h set default delay and rate (PCjr and some PS/2)
            01h increase delay before repeat (PCjr)
            02h decrease repeat rate by factor of 2 (PCjr)
            03h increase delay and decrease repeat rate (PCjr)
            04h turn off typematic repeat (PCjr and some PS/2)
            05h set repeat rate and delay (AT,PS)
                BH = delay value (00h = 250ms to 03h = 1000ms)
                BL = repeat rate (00h=30/sec to 0Ch=10/sec [def] to 1Fh=2/sec)
            06h get current typematic rate and delay (newer PS/2s)
                Return: BL = repeat rate (see above)
                        BH = delay (see above)
Note:   use INT 16/AH=09h to determine whether some of the subfunctions are
          supported