The future of the world chess championship was in question Friday when a player did not show up for the fifth game and threatened to withdraw from the match after he was accused of cheating and locked out of his private bathroom. Vladimir Kramnik, a Russian, was accused by the manager for his opponent, Veselin Topalov of Bulgaria, of taking too many bathroom breaks _ an apparent suggestion that he was secretly using a technical device or a computer program to help him with his moves. Kramnik, the Classical World Champion, had been leading Topalov, the World Chess Champion, 3-1...