INT D4 - PC-MOS/386 v5.01 - GET/SET EXTENDED DIRECTORY INFORMATION
        AH = 03h
        AL = subfunction (00h get, 01h set)
        DS:(E)DX -> pathname
        ES:(E)BX -> 10-byte buffer for directory information (see below)
Return: CF clear if successful
            AL = permitted access level for file (00h-03h)
            ES:(E)BX -> modified buffer (AL=01h on entry)
        CF set on error
            AX = error code (see INT 21/AH=59h)
Notes:  BX/DX are used in V86 mode, EBX/EDX in native mode
        the file class cannot be changed for files because it affects the
          encryption method, but directories can have their classes changed

Format of directory information:
Offset  Size    Description
 00h    BYTE    reserved (0)
 01h    BYTE    file class ('A'-'Z' or 00h)
 02h    DWORD   user ID of file creator
 06h    WORD    file creation time (see INT 21/AX=5700h)
 08h    WORD    file creation date (see INT 21/AX=5700h)

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