Reuters: When Lamborghini and Hummer try getting in on the action, you know greener cars have come of age. The makers of $400,000 supercars and flashy sports utility vehicles find themselves trying to keep up with tiny, fuel efficient new models at this week’s Geneva auto show as toughening pollution laws put the focus on small, light and thrifty. Hummer, the rugged U.S. troops transporter that has become popular with Hollywood stars, is showing a version of its HX concept vehicle that …