RIO DE JANEIRO >> Andy Murray is making a habit of accomplishing things that hadn't been done in a while.Or ever.Murray became the first tennis player in Olympic history with two singles gold medals, winning his second in a row by wearing down Juan Martin del Potro of Argentina 7-5, 4-6, 6-2, 7-5 at the Rio de Janeiro Games in a final that lasted a tad more than 4 hours Sunday.