use using instead of typedef (and use base cstr)

STL_Extension/include/CGAL/Base_with_time_stamp.h

@@ -20,7 +20,9 @@ template <typename Base>
 class Base_with_time_stamp : public Base {
   std::size_t time_stamp_ = -1;
 public:
-  typedef CGAL::Tag_true Has_timestamp;
+  using Base::Base;
+
+  using Has_timestamp = CGAL::Tag_true;
 
   std::size_t time_stamp() const {
     return time_stamp_;