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

(cherry picked from commit 077b5aec9ede78034ba2ec4838b72e8121dab7ce)

src/common/Utilities/Util.h

@@ -334,9 +334,9 @@ class HookList
     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;
         }
 
@@ -346,7 +346,7 @@ class HookList
             _container.emplace_back(std::forward<Args&&>(args)...);
         }
 
-        size_t size()
+        size_t size() const
         {
             return _container.size();
         }