INT 21 U - DR-DOS 5.0-6.0 internal - SET EXTENDED FILE ATTRIBUTES
        AX = 4305h
        DS:DX -> ASCIZ filename
        ???
Return: CF clear if successful
        CF set on error
            AX = error code (see AH=59h)
Desc:   this function allows the extended attributes, and optionally the
          encrypted password, of a file to be set.
Note:   this function is only supported by DR-DOS 5.0 and 6.0 and DRMDOS 5.1
SeeAlso: AX=4304h,AX=4311h

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