At the Public Theater’s 2013 gala at the Delacorte Theater in Central Park last night, Sting, Steve Martin and Meryl Streep had prime seats for a one-night-only performance of “The Pirates of Penzance,” starring Kevin Kline as the Pirate King and Martin Short as Major-General Stanley, a sure recipe for hilarity. Streep took the stage before the performance to say a few words about her friend Nora Ephron. Streep recalled a dinner with Ephron. “I bubbled to our tablemates, ’Bon Appetit,’” Streep said, doing a perfect imitation of Julia Child. “And she gave me a sideways look and said, ’I have a thought.’”