INT 21 - DOS 3.1+ - IOCTL - CHECK IF BLOCK DEVICE REMOTE
        AX = 4409h
        BL = drive number (00h = default, 01h = A:, etc)
Return: CF clear if successful
            DX = device attribute word
                bit 15: drive is SUBSTituted
                bit 12: drive is remote
                bit  9: direct I/O not allowed
        CF set on error
            AX = error code (01h,0Fh) (see AH=59h)
Note:   on local drives, DX bits not listed above are the attribute word from
          the device driver header (see AH=52h); for remote drives, the other
          bits appear to be undefined for DOS versions prior to 5.0 (they are
          all cleared in DOS 5+)
SeeAlso: AX=4400h,AX=4408h,AX=440Ah,INT 2F/AX=122Bh

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