Restore everything when a function pointer is NULL

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%40991

test/testdyngl.c

@@ -106,6 +106,8 @@ int main(int argc,char *argv[])
 		printf("Unable to init SDL : %s\n",SDL_GetError());
 		exit(1);
 	}
+
+	atexit(SDL_Quit);
 	
 	if (SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER,1)<0)
 	{