SALT LAKE CITY — When Utah’s new federal courthouse opened last week, it came with security improvements that are becoming standard around the country: separate entrances and elevators for judges, defendants and the public; bullet-resistant glass and paneling; and vehicle barricades to keep car bombs at bay. Even the design of the courtrooms, with plenty of sunlight and space, can help calm witnesses or defendants in high-stress cases, some judges believe. But nothing can prevent every violent courtroom …