message: make Simplex_handle and Simplex_hash public for fibration purpose
diff: @@ -37,7 +37,8 @@ namespace coxeter_triangulation {
  */
  template <class Triangulation_>
  class Manifold_tracing {
  - typedef typename Triangulation_::Simplex_handle Simplex_handle;
  + public:
  + using Simplex_handle = typename Triangulation_::Simplex_handle;
  struct Simplex_hash {
  typedef Simplex_handle argument_type;
  