By Steve Keating TULSA, Oklahoma (Reuters) – Justin Thomas was clinging to the second round clubhouse lead at the wind-whipped PGA Championship on Friday, as Rory McIlroy was being blown down the leaderboard. With Southern Hills buffeted by gusts of up to 40 mph (65 kph), Thomas was unfazed as he mixed four birdies, including one at his final hole, with a single bogey to return a second consecutive three-under 67 to sit on six-under at the midway point bumping the Northern Irishman from top spot. Out in the afternoon wave, McIlroy started his round with only Thomas one shot in front. But after…