INT 21 - DOS 2+ - "CHMOD" - SET FILE ATTRIBUTES
        AX = 4301h
        CX = new attributes
            bit 7: shareable (Novell NetWare)
                6: unused
                5: archive
                4: directory
                3: volume label
                   execute-only (Novell NetWare)
                2: system
                1: hidden
                0: read-only
        DS:DX -> ASCIZ filename
Return: CF clear if successful
            AX destroyed
        CF set on error
            AX = error code (01h,02h,03h,05h) (see AH=59h)
Notes:  will not change volume label or directory attribute bits, but will
          change the other attribute bits of a directory (the directory
          bit must be cleared to successfully change the other attributes of a
          directory, but the directory will not be changed to a normal file as
          a result)
        MSDOS 4.01 reportedly closes the file if it is currently open
        for security reasons, the Novell NetWare execute-only bit can never
          be cleared; the file must be deleted and recreated
        under the FlashTek X-32 DOS extender, the filename pointer is in DS:EDX
SeeAlso: AX=4311h,INT 2F/AX=110Eh