Aware that many people doubt he is as good a golfer as he claims, President Clinton hit the links at the Farm Neck Golf Club in Oak Bluffs, Mass., as hard as he could Friday, anxious to prove the naysayers wrong. It didn’t happen. The president, who’s vacationing at Martha’s Vineyard, shot an 86, 14 above par. At the same course Monday, Clinton shot a 79 despite two extra swings at the first hole. At least, that’s his story, and he’s sticking to it. The president is looking to make up for the five months of tee time he lost to a knee injury suffered at golfer Greg Norman’s home in Florida.