By Larry Fine RYE, New York (Reuters) - Winning a major is its own reward, but rivalries, rankings and next year's Rio Olympics were also on the mind of contenders at the Women's PGA Championship starting on Thursday at Westchester Country Club. World number one Lydia Ko of New Zealand zoomed to the top of the rankings at the tender age of 17 and the 18-year-old is gunning for her first major. "We're just enjoying ourselves and trying to make as many birdies as we can," said Ko, who admitted it would be neat to get the golden putter given by her sponsor Callaway for winning a major. More...