Brian Dennehy, the burly actor who has won Tony awards for both his Willy Loman in “Death of a Salesman” and his James Tyrone in “Long Day’s Journey Into Night,” is making a return visit to the Stratford Shakespeare Festival in Ontario this summer. He’s appearing in two shows running through October, Shakespeare’s “Twelfth Night” and Harold Pinter’s “The Homecoming.” New York Times theater critic Charles Isherwood tells Jeff Spurgeon about what makes him a singular actor.