Watch the video here   Earning himself several laughs from the audience, Bruce Willis used his appearance on the “Late Show with David Letterman” Thursday (August 30) to poke fun at the Kristen Stewart and Robert Pattinson breakup. The "Looper" star parodied the highly-publicized split with a clip from his supposed new "Die Hard 5" flick, titled "Twi-Hard: With A Vengeance". In the spot B…