Steve Martin and Martin Short will christen Hancher’s stage at the start of a wild and crazy first season for the University of Iowa’s new $113 million performing arts center. The comedians who rocketed to stardom via “Saturday Night Live” will perform together for Hancher’s Sept. 24 gala. Steve Martin, a crackerjack banjo player, also will perform with his bluegrass band, the Steep Canyon Rangers. Don’t be fooled by their name for the show: “An Evening You’ll Forget for the Rest of Your Life.” Chuck Swanson, Hancher’s executive director, promises the event filled with Champagne and surprises will be an evening to remember. “It is just fabulous, they’re so good,” said Swanson, who saw the pair perform in Milwaukee.