Resolve some quirks with (wield) item meshes for nodes (#15654)

src/client/mapblock_mesh.h

@@ -62,6 +62,11 @@ struct MeshMakeData
 	void fillBlockDataBegin(const v3s16 &blockpos);
 	void fillBlockData(const v3s16 &bp, MapNode *data);
 
+	/*
+		Prepare block data for rendering a single node located at (0,0,0).
+	*/
+	void fillSingleNode(MapNode data, MapNode padding = MapNode(CONTENT_AIR));
+
 	/*
 		Set the (node) position of a crack
 	*/