LOS ANGELES — Bill Paxton, the versatile actor who appeared in films including “Aliens” and “Titanic” and played a polygamist on HBO’s “Big Love,” has died from complications following heart surgery. He was 61.A representative for his family released a statement asking for privacy and saying, “Bill’s passion for the arts was felt by all who knew him, and his warmth and tireless energy were undeniable.”With a Texas twang and grizzled visage, Paxton often found himself playing military men and cowboys.