Use make_intrusive/make_shared for smart pointer construction.

src/util/io/reader.hpp

@@ -200,7 +200,7 @@ class Reader {
  */
 template <typename T>
 intrusive_ptr<T> read_new(Reader& reader) {
-  return intrusive(new T());
+  return make_intrusive<T>();
 }
 
 /// Update the 'index' member of a value for use by IndexMap