AUSTIN, Texas (Reuters) -Formula One and the championship-leading Red Bull team mourned the death of the energy drink company’s Austrian founder Dietrich Mateschitz on Saturday at the age of 78. Red Bull Racing principal Christian Horner confirmed the news ahead of qualifying for the U.S. Grand Prix in Austin, Texas, where the team can clinch a fifth constructors’ championship. Red Bull’s Max Verstappen has already won the drivers’ title for the second year in a row. “What he (Mateschitz) achieved and what he’s done for so many people around the world, across different sports, is second to non…