Avoid reading non-32bpp sprites twice where possible

Try to avoid unnecessary over-reading

src/spriteloader/spriteloader.hpp

@@ -74,7 +74,7 @@ public:
 	 * @param load_32bpp  True if 32bpp sprites should be loaded, false for a 8bpp sprite.
 	 * @return Bit mask of the zoom levels successfully loaded or 0 if no sprite could be loaded.
 	 */
-	virtual uint8 LoadSprite(SpriteLoader::Sprite *sprite, SpriteFile &file, size_t file_pos, SpriteType sprite_type, bool load_32bpp) = 0;
+	virtual uint8 LoadSprite(SpriteLoader::Sprite *sprite, SpriteFile &file, size_t file_pos, SpriteType sprite_type, bool load_32bpp, uint count) = 0;
 
 	virtual ~SpriteLoader() { }
 };