DOCUMENTARY PREMIERE: The indefatigable Carl Reiner is behind this new, defiantly cheerful documentary, in which he visits with fellow nonagenarians to talk about their approaches to life, love, diet, exercise, hobbies, and not dying. (My own father, even in his 70s, was fond of saying, “At my age, I don’t even buy green bananas.”) In one segment, Reiner sits with Mel Brooks and Norman Lear, all of whom have been mutual friends for more than 65 years – and all three of th