NAME
        GPD_SETTRIGGER -- Set the conditions for a game port report

   FUNCTION
        This command sets what conditions must be met by a game
        port unit before a pending read request will be satisfied.
        These conditions, called triggers, are independent -- that
        any one occurs is sufficient to queue a game port report to
        the read queue.    these conditions are inquired with
        AskTrigger.

        This command always executes immediately.

   IO REQUEST
        io_Message      mn_ReplyPort set if quick I/O is not possible
        io_Device       preset by the call to opendevice
        io_Unit         preset by the call to opendevice
        io_Command      GPD_SETTRIGGER
        io_Flags        IOB_QUICK set if quick I/O is possible
        io_Length       sizeof(gamePortTrigger)
        io_Data         a structure of type gameporttrigger, which
                        has the following elements
            gpt_Keys -
                    GPTB_DOWNKEYS set if button down transitions
                    trigger a report, and GPTB_UPKEYS set if button up
                    transitions trigger a report
            gpt_Timeout -
                    a time which, if exceeded, triggers a report;
                    measured in vertical blank units (60/sec)
            gpt_XDelta  -
                    a distance in x which, if exceeded, triggers a
                    report
            gpt_YDelta  -
                    a distance in x which, if exceeded, triggers a
                    report