and calls to index(Face_handle ) in Triangulation_data_structure_2.h
to fit the needs of the extended triangulatin data structure of
additively weighted Voronoi diagram
-suppression of Triangulation_face_2 and Triangulation_vertex_2 classes
the TDS and Triangulation now have the same faces and vertices
defined in TDS class
as well as Face_handle and Vertex_handle classes
-supression of Triangulation_default_data_structure_2
and Triangulation_data_structure_using_list_2. There is now only
one Triangulation_data_structure_2 (which for the moment is still
using list).