INT 21 - DOS 1+ - RENAME FILE USING FCB
        AH = 17h
        DS:DX -> modified FCB (see also AH=0Fh)
                the old filename ('?' wildcards OK) is in the standard location
                while the new filename ('?' wildcards OK) is stored in the 11
                bytes beginning at offset 11h
Return: AL = status
            00h successfully renamed
            FFh no matching files,file is read-only, or new name already exists
Notes:  subdirectories may be renamed using an extended FCB with the
          appropriate attribute, as may volume labels
        DR-DOS checks password attached with AX=4303h before permitting rename
SeeAlso: AH=0Fh,AH=13h,AX=4303h,AH=56h,INT 2F/AX=1111h

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