Given their curious joint histories – first as famous feuders, then, finally, as fast (though superficial) friends – this new edition of Oprah Winfrey’s profile series, focusing on the late-night TV host who spent years making fun of her, should be pretty interesting. Especially so, since Letterman rarely sits still for this sort of thing – and even then, isn’t likely to take it seriously throughout. But be prepared, because Winfrey does get him to open up about som