quit on ESC

Of my three patches, this is the one I am the least confident in. On my system (OS X 10.6), playBanana doesn't quit when the escape key is pressed and I have no idea why. Since this is a part of gloss which I like, I wanted to patch playBanana so that it would quit as expected. I don't know if abruptly quitting via exitSuccess will have any adverse effects on gloss or reactive-banana, but I haven't encountered any yet.