Core/Util: avoid one useless copy when adding stuff into a HookList

src/common/Utilities/Util.h

@@ -337,13 +337,13 @@ class HookList final
     public:
         typedef typename ContainerType::iterator iterator;
 
-        HookList<T>& operator+=(T t)
+        HookList<T>& operator+=(T&& t)
         {
-            _container.push_back(t);
+            _container.push_back(std::move(t));
             return *this;
         }
 
-        size_t size()
+        size_t size() const
         {
             return _container.size();
         }