DIED. John Dexter, 64, versatile British director of theater and opera; of a heart attack; in London. Equally at home with contemporary and repertory plays, Dexter won Tonys in 1975 and 1988 for his Broadway productions of Equus and M. Butterfly. He served as an associate director of Britain's National Theatre under Laurence Olivier. Dexter staged Dialogues of the Carmelites and The Abduction from the Seraglio with New York City's Metropolitan Opera.