By David Shepardson (Reuters) -Volkswagen AG and its Porsche AG unit have agreed to a class-action settlement worth at least $80 million to resolve claims it skewed emissions and fuel economy data on 500,000 Porsche vehicles in the United States, court documents show. The settlement, filed in U.S. District Court in San Francisco, must be approved by a federal judge. It covers 2005 through 2020 model year Porsche vehicles after owners accused the automaker of physically altering test vehicles that affected emissions and fuel economy results. Owners of eligible vehicles will receive payments of …