Set current time (INT 21h, 2Dh)

        Entry:
          AH = 2Dh
          CH = hours
          CL = minutes
          DH = seconds
          DL = hundredths of seconds
        Return:
          AL = 00h if no error
             = FFh if bad value sent to routine
               (DOS 3.3 also sets CMOS clock)

        Note: DOS 3.3+ also sets CMOS clock