Bugfix of case sent to list on 2011-06-27 by Phillip. To detect if geometry is within another, we use "point_on_border". We used a mid-point there (necessary for intersections), but, from now on, if there are no intersections, we should not use the mid-point because of robustness issues.
In other words, we should use the same point for both intersection-->side and within-->side.