NAME
    CMD_UPDATE -- Terminate the writing of a clip to the clipboard.

FUNCTION
    Indicate to the clipboard that the previous write commands are
    complete and can be used for any pending pastes (reads).  This
    command cannot be issued while any of the write commands are
    pending.

IO REQUEST
    io_Message      mn_ReplyPort set up
    io_Device       preset by opendevice
    io_Unit         preset by opendevice
    io_Command      CMD_UPDATE
    io_ClipID       the ClipID of the write

RESULTS
    io_Error        non-zero if an error occurred