Implemented load audio and music files as well the basic audio playback

functionality.

include/Renderer.h

@@ -19,7 +19,7 @@ void render_clear(const Renderer *renderer, SDL_Color color);
 void render_texture(const Renderer *renderer, SDL_Texture *texture, float x,
                     float y, float w, float h);
 void swap_buffers(const Renderer *renderer);
-void destroy_renderer(Renderer *renderer);
+void destroy_renderer(Renderer **renderer);
 
 #ifdef __cplusplus
 }