Tear out mesh writers

Totally unused in Minetest

source/Irrlicht/CSceneManager.cpp

@@ -862,13 +862,6 @@ ISkinnedMesh* CSceneManager::createSkinnedMesh()
 	return new CSkinnedMesh();
 }
 
-//! Returns a mesh writer implementation if available
-IMeshWriter* CSceneManager::createMeshWriter(EMESH_WRITER_TYPE type)
-{
-	return 0;
-}
-
-
 // creates a scenemanager
 ISceneManager* createSceneManager(video::IVideoDriver* driver, gui::ICursorControl* cursorcontrol)
 {

source/Irrlicht/CSceneManager.h

@@ -168,9 +168,6 @@ namespace scene
 		//! Returns type of the scene node
 		ESCENE_NODE_TYPE getType() const override { return ESNT_SCENE_MANAGER; }
 
-		//! Returns a mesh writer implementation if available
-		IMeshWriter* createMeshWriter(EMESH_WRITER_TYPE type) override;
-
 		//! Get a skinned mesh, which is not available as header-only code
 		ISkinnedMesh* createSkinnedMesh() override;