New get_trapezoids() implementation. Maybe heavier but it doesn't fail with some versions of GCC like the one provided by Boost.Polygon. #1965

xs/src/Polygon.hpp

@@ -15,6 +15,8 @@ typedef std::vector<Polygon> Polygons;
 class Polygon : public MultiPoint {
     public:
     operator Polygons() const;
+    Point& operator[](Points::size_type idx);
+    const Point& operator[](Points::size_type idx) const;
     Point last_point() const;
     Lines lines() const;
     void lines(Lines* lines) const;