Merge branch 'master' into boost-medialaxis

Conflicts:
	lib/Slic3r/Layer/Region.pm
	xs/src/ExPolygon.cpp
	xs/src/Point.cpp
	xs/src/Point.hpp
	xs/src/TriangleMesh.cpp
	xs/t/01_trianglemesh.t

xs/src/Line.hpp

@@ -17,6 +17,7 @@ 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);