Added two Roadmap items

- Correct the _locate()
- Correct the way functors access the segment traits.

Arrangement_on_surface_2/include/CGAL/Arr_polyline_traits_2.h

@@ -28,6 +28,13 @@
  *       to the user.
  */
 
+/*
+ * Roadmap: In all functors, replace the member m_seg_traits with an instance
+ *          of Arr_polyline_traits. Then use the member function
+ *          segment_traits_2() to get whatever needed from the segment traits.
+ *          See the implementation of Equal_2
+ */
+
 #ifndef CGAL_ARR_POLYLINE_TRAITS_2_H
 #define CGAL_ARR_POLYLINE_TRAITS_2_H
 
@@ -1555,6 +1562,12 @@ public:
   //@}
 
 private:
+  /*
+   * Roadmap:
+   *  - _locate() should return an iterator to the located segment
+   *  - Should not get m_seg_traits as an argument, instead it should be called
+   *    as a member function of the Arr_polyline_traits_2 object.
+   */
   /*!
    * Return the index of the segment in the polyline that contains the
    * point q in its x-range. The function performs a binary search, so if the