graphical ->draw_poly: points=chain|vector,
closed=[bool], fill=[colour|{foreground,background}]*Draw/fill a polygon. Points is a chain
object or vector
object containing the points though which the polyline is drawn. If
closed is @on,
a line is drawn from the last to the first point. If fill is specified,
the interior is filled with the given colour.
This method is part of the user-defined graphics infra-structure
described with graphical->_redraw_area
and should not be called outside this context.
