Codechange: Make the simple Malloc sprite allocator globally usable.

src/spritecache.cpp

@@ -808,6 +808,14 @@ static void *AllocSprite(size_t mem_req)
 	}
 }
 
+/**
+ * Sprite allocator simply using malloc.
+ */
+void *SimpleSpriteAlloc(size_t size)
+{
+	return MallocT<byte>(size);
+}
+
 /**
  * Handles the case when a sprite of different type is requested than is present in the SpriteCache.
  * For ST_FONT sprites, it is normal. In other cases, default sprite is loaded instead.