Rest of the path chaining has been replaced with the new algorithm.

PolylineCollection.cpp/hpp was removed, use Polylines instead.
Various first_point() / last_point() now return references, not copies.

src/libslic3r/CMakeLists.txt

@@ -131,8 +131,6 @@ add_library(libslic3r STATIC
     PolygonTrimmer.hpp
     Polyline.cpp
     Polyline.hpp
-    PolylineCollection.cpp
-    PolylineCollection.hpp
     Print.cpp
     Print.hpp
     PrintBase.cpp