A minor update to post-game behavior

Hi, all. I've updated Story Mode to handle some post-game situations more gracefully. When an Inform 7 game ends, the player is presented with what are called the "final question options." Because of Story Mode, players may need to UNDO or RESUME, depending on whether the mode is active. The "final question options" did not always reflect the current state of the game, especially after multiple uses of *UNDO* near the end.

I've made the needed tweaks for Story Mode to deal with end-of-game situations in a more intuitive way. No bugfixes AFAIK, just this one adjustment.

If you need help using Story Mode in your Inform game, get in touch! I'd be happy to help.

-drew