NEW YORK – You’ve got to be at the top of your game to be a one-name model: There’s Iman, Naomi, Gisele – Barbie. The 11.5-inch plastic doll is still on top as a high-fashion muse as she approaches her 50th birthday, and will make her New York Fashion Week catwalk debut on Saturday in 50 outfits by the country’s top designers.