Fix overflow in distance_to(Line*). It was affecting Douglas-Peucker causing massive loss of geometry. Includes regression test and a couple wkt() implementations

xs/src/Line.hpp

@@ -16,6 +16,7 @@ class Line
     Point b;
     Line() {};
     explicit Line(Point _a, Point _b): a(_a), b(_b) {};
+    std::string wkt() const;
     operator Polyline() const;
     void scale(double factor);
     void translate(double x, double y);