Updated the release notes for 2D Arrangements for 4.13.

Installation/CHANGES.md

@@ -252,6 +252,23 @@ g
 -   Added a read-write property map to convert on-the-fly geometric
     objects from Cartesian kernels.
 
+### 2D Arrangements
+
+-   Refracted and fixed the `graph_traits` for the dual of an arrangement of the
+    following types:
+    `Arrangement_on_surface_2`,
+    `Arrangement_2`,
+    `Arrangement_on_surface_with_history_2`, and
+    `Arrangement_with_history_2`.
+
+-   **Breaking change**: The old `<CGAL/graph_traits_Dual_Arrangement_2.h>`
+    header file has been replaced by the four header files below; each defines
+    the `graph_traits` for dual of the corresponding arrangement type.
+    `<CGAL/graph_traits_dual_arrangement_on_surface_2.h>`,
+    `<CGAL/graph_traits_dual_arrangement_2.h>`,
+    `<CGAL/graph_traits_dual_arrangement_on_surface_with_history_2.h>`, and
+    `<CGAL/graph_traits_dual_arrangement_with_history_2.h`.
+
 
 Release 4.12
 ------------