Int 2F Fn D103  - Mdebug Command Driver - Execute Key In The Monitor       [G]

   AX = D103h
   BX = key code (like result of an interrupt 16h call)
   CX = 0 -> the cursor is in the ASCII column of the monitor
   CX = 1 -> the cursor is in one of the hex fields of the monitor
   DS:SI -> MDEBUG data structure (see AX=D102h)
   ES:DI -> actual byte in the monitor

Return: AL = FFh
   AH = return code
       00h key processed, read next key
       01h leave MDEBUG popup session
       02h leave MDEBUG popup session and automatically popup again if DOS
       is not busy
       03h signal an error (beep)
       04h driver has redefined the key, proceed with the new key
       BX = new key code
       MDEBUG will not pass the new key to the command driver(s)
      else treat like code 00h

Note:  this function must end with a far call to the old INT 2F handler (with
     registers unchanged) if the driver does not support the key in BX.
     Otherwise, the driver must not chain to the old INT 2F.

See Also: AX=D104h