Feature #7962: Significantly improve sprite sorter performance

src/viewport_sprite_sorter.h

@@ -36,7 +36,7 @@ struct ParentSpriteToDraw {
 	int32 top;                      ///< minimal screen Y coordinate of sprite (= y + sprite->y_offs), reference point for child sprites
 
 	int32 first_child;              ///< the first child to draw.
-	bool comparison_done;           ///< Used during sprite sorting: true if sprite has been compared with all other sprites
+	uint32 order;                   ///< Used during sprite sorting
 };
 
 typedef std::vector<ParentSpriteToDraw*> ParentSpriteToSortVector;