INT 13 - FLOPPY DISK - DETECT DISK CHANGE (XT 1/10/86 or later,XT286,AT,PS)
        AH = 16h
        DL = drive number
Return: CF clear if change line inactive
            AH = 00h (disk not changed)
        CF set if change line active
            AH = 06h change line active or not supported
               = 80h drive not ready or not present
Note:   call AH=15h first to determine whether the drive supports a change
          line