INT 21 - DOS 3.x+ internal - GET AND SET EXTENDED CONTROL-BREAK CHECKING STATE
        AX = 3302h
        DL = new state
             00h for OFF or 01h for ON
Return: DL = old state of extended BREAK checking
Note:   this function does not use any of the DOS-internal stacks and may thus
          be called at any time; one possible use is modifying Control-Break
          checking from within an interrupt handler or TSR