SDL: Split quit() method into deinit() so error codes could be returned.

svn-id: r49131

backends/platform/sdl/main.cpp

@@ -63,7 +63,7 @@ int main(int argc, char *argv[]) {
 
 	// Invoke the actual ScummVM main entry point:
 	int res = scummvm_main(argc, argv);
-	g_system->quit();	// TODO: Consider removing / replacing this!
+	((OSystem_SDL *)g_system)->deinit();
 	return res;
 }