NEW YORK (Reuters) - Actor Robert Wagner says he was so distraught over the break-up of his first marriage to actress Natalie Wood that he pondered suicide and would sit with a gun outside the home of her lover, Warren Beatty, intent on killing him. "Pieces of My Heart," Wagner's autobiography released this week, reveals details of his career and life, including the split with Wood, their decision to remarry a decade later and her drowning death in 1981. "I was pretty young, and I don't think I could have ever gone through with that act, but I was pretty...