INT 21 - DOS 2+ - EXTENDED BREAK CHECKING
        AH = 33h
        AL = subfunction
            00h get current extended break state
                Return: DL = current state, 00h = off, 01h = on
            01h set state of extended  Break checking
                DL = 00h off, check only on character I/O functions
                     01h on, check on all DOS functions
Note:   under DOS 3.1+, this function does not use any of the DOS-internal and
          may thus be called at any time