NAME
        CreateContext -- create a place for GadTools context data. (V36)

   SYNOPSIS
        gad = CreateContext(glistpointer);
        D0                  A0

        struct gadget *createcontext(struct gadget **);

   FUNCTION
        Creates a place for GadTools to store any context data it might
        need for your window.  In reality, an unselectable invisible
        gadget is created, with room for the context data.
        This function also establishes the linkage from a glist type
        pointer to the individual gadget pointers.  Call this function
        before any of the other gadget creation calls.

   INPUTS
        glistptr - address of a pointer to a gadget, which was previously
                   set to NULL.  When all the gadget creation is done, you may
                   use that pointer as your NewWindow.FirstGadget, or
                   in intuition.library/addglist(),
                   intuition.library/refreshglist(), freegadgets(), etc.

   RESULT
        gad - pointer to context gadget, or NULL if failure.

   EXAMPLE

        struct gadget *gad;
        struct gadget *glist = null;
        gad = CreateContext(&glist);
        /*  Other creation calls go here */
        if (gad)
        {
            myNewWindow.FirstGadget = glist;
            if ( myWindow = OpenWindow(&myNewWindow) )
            {
                GT_RefreshWindow(win,NULL);
                /* other stuff */
                CloseWindow(myWindow);
            }
        }
        FreeGadgets(glist);