Recalculate normals for cached meshes.

Check if mesh is here before adding to meshcollector.

Fix deleting the meshes.

src/client.h

@@ -447,6 +447,7 @@ class Client : public con::PeerHandler, public InventoryManager, public IGameDef
 	virtual ICraftDefManager* getCraftDefManager();
 	virtual ITextureSource* getTextureSource();
 	virtual IShaderSource* getShaderSource();
+	virtual scene::ISceneManager* getSceneManager();
 	virtual u16 allocateUnknownNodeId(const std::string &name);
 	virtual ISoundManager* getSoundManager();
 	virtual MtEventManager* getEventManager();