Fix Clang warnings about hidden virtual methods

components/terrain/quadtreenode.hpp

@@ -40,7 +40,7 @@ namespace Terrain
         inline unsigned int getNumChildren() const { return _children.size(); }
 
         // osg::Group::addChild() does a lot of unrelated stuff, but we just really want to add a child node.
-        void addChild(QuadTreeNode* child)
+        void addChildNode(QuadTreeNode* child)
         {
             // QuadTree node should not contain more than 4 child nodes.
             // Reserve enough space if this node is supposed to have child nodes.

components/terrain/quadtreeworld.cpp

@@ -165,7 +165,7 @@ public:
             if (child)
             {
                 boundingBox.expandBy(child->getBoundingBox());
-                parent->addChild(child);
+                parent->addChildNode(child);
             }
         }