Enabled SDL_image's support for PNG and TIFF files and improved the

AssetManager with a hashing function, a linked list structure to store
the hashes as well as a reference counter to support multiple users
sharing the same asset.

include/GameEngine.h

@@ -7,18 +7,26 @@
 #include "reusable_ids.h"
 #include <stdbool.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif // !__cplusplus
+
 bool init_game(const char *game_name, int window_width, int window_height,
                SDL_Color window_background_color, bool full_screen);
 bool game_running();
 ObjectID add_object(void *object, EventHandlerPtr eh, UpdateFuncPtr uf,
                     RenderFuncPtr rf);
-void remove_object(ObjectID id);
+void remove_object(ObjectID *id);
 AssetID load_asset(const char *path, AssetType type);
 void render_texture_asset(AssetID id, float x, float y, float w, float h);
-void close_asset(AssetID id);
+void close_asset(AssetID *id);
 void handle_events();
 void update();
 void render();
 void close_game();
 
+#ifdef __cplusplus
+}
+#endif // !__cplusplus
+
 #endif // !GAME_H