add missing examples in doc

Triangulation_2/doc/Triangulation_2/examples.txt

@@ -15,4 +15,5 @@
 \example Triangulation_2/terrain.cpp
 \example Triangulation_2/triangulation_prog1.cpp
 \example Triangulation_2/voronoi.cpp
+\example Triangulation_2/copy_triangulation_2.cpp
 */

Triangulation_3/doc/Triangulation_3/examples.txt

@@ -9,4 +9,5 @@
 \example Triangulation_3/fast_location_3.cpp
 \example Triangulation_3/find_conflicts_3.cpp
 \example Triangulation_3/regular_3.cpp
+\example Triangulation_3/copy_triangulation_3.cpp
 */