SceneGraph: properly forward references in addChild()/addFeature().

doc/changelog.dox

@@ -404,6 +404,9 @@ See also:
 -   Improved @ref TextureTools::distanceField() to work better on shader
     compilers that have problems compiling nested loops (WebGL implementations,
     some ES2 devices)
+-   @ref SceneGraph::AbstractObject::addFeature() and
+    @ref SceneGraph::Object::addChild() were not properly forwarding reference
+    arguments
 
 @subsection changelog-latest-docs Documentation
 

src/Magnum/SceneGraph/AbstractObject.h

@@ -111,7 +111,7 @@ template<UnsignedInt dimensions, class T> class AbstractObject
          * Calling `object.addFeature<MyFeature>(args...)` is equivalent to
          * `new MyFeature{object, args...}`.
          */
-        template<class U, class ...Args> U& addFeature(Args... args) {
+        template<class U, class ...Args> U& addFeature(Args&&... args) {
             return *(new U{*this, std::forward<Args>(args)...});
         }
 

src/Magnum/SceneGraph/Object.h

@@ -193,7 +193,7 @@ template<class Transformation> class Object: public AbstractObject<Transformatio
          * Calling `object.addChild<MyObject>(args...)` is equivalent to
          * `new MyObject{args..., &object}`.
          */
-        template<class T, class ...Args> T& addChild(Args... args) {
+        template<class T, class ...Args> T& addChild(Args&&... args) {
             return *(new T{std::forward<Args>(args)..., this});
         }