eliminate tail recursion in game.runloop() to prevent stack overflow

Michael,

When I was testing the launcher, I noticed that it was calling itself and using more stack space each time I launched a game and went back to the menu.  This could cause problems if the game runs longer, especially if starting a Python game.

This change should resolve the problem, but I have been unable to test it since I'm not running any Python games on my cabinet.

-Tom