Merchant-Ivory's lush adaptation of E.M. Forster's novel of romantic struggle against Edwardian repression is the best possible version of those PBS dramas your mom likes to watch--better, even, because this one has full frontal male nudity.   Starring Helena Bonham Carter, Julian Sands, Maggie Smith, Denholm Elliott, Daniel Day-Lewis, Judi Dench, and Simon Callow. Written by Ruth Prawer Jhabvala, and directed by James Ivory.