Bill Clinton showed his doctors yesterday that he knows how to follow orders — stopping by the hospital that diagnosed his heart problem and wowing the crowd with his stunning weight loss. As these photos show, there was a lot less of Bill Clinton on display at Westchester County Medical Center in Valhalla, where the ex-president cut the ribbon on a new cardiac center. Just four months ago, Clinton flashed his best greasy-burger smile at a Post photographer during an outing to the Central Park Zoo. But yesterday, he was a shadow of his former self, thanks to a strict...