Ironweed What do you do, when what you have done is so bad you can`t forgive yourself? William Kennedy`s own screenplay of one of his Albany novels (The other two are BILLY PHELAN`S GREATEST GAME and LEGS.)offers one answer. Jack Nicholson and Meryl Streep give sterling performances as Francis and Helen; Tom Waits and Fred Gwynne are merely outstanding; the rest just shine. The movie is laced with baseball references. It`s late in the 9th, and Francis is down a dozen runs. Can he pull it out? As Yogi reminds us: "It ain`t over `til it`s over."