NAME
        ScrollVPort -- Reinterpret RasInfo information in viewport to reflect
                        the current Offset values.

   SYNOPSIS
        ScrollVPort( vp )
                     a0

        void ScrollVPort(struct viewport *vp);

   FUNCTION
        After the programmer has adjusted the Offset values in
        the RasInfo structures of viewport, change the
        the copper lists to reflect the the Scroll positions.
        Changing the bitmap ptr in rasinfo and not changing the
        the Offsets will effect a double buffering affect.

   INPUTS
       vp - pointer to a viewport structure
             that is currently be displayed.
   RESULTS
        modifies hardware and intermediate copperlists to reflect
        new RasInfo

   BUGS
       pokes not fast enough to avoid some visible hashing of display (V37)
        This function was re-written in V39 and is ~10 times faster than
        before.

   SEE ALSO
        makevport() mrgcop() loadview()  graphics/view.h