message: Make Kernel available publicly for tests purpose
diff: @@ -154,8 +154,10 @@ class Alpha_complex_3d {
  using Kernel = CGAL::Periodic_3_regular_triangulation_traits_3<Predicates>;
  };
  + public:
  using Kernel = typename Kernel_3<Predicates, Weighted, Periodic>::Kernel;
  + private:
  using TdsVb = typename std::conditional<Periodic, CGAL::Periodic_3_triangulation_ds_vertex_base_3<>,
  CGAL::Triangulation_ds_vertex_base_3<>>::type;
  