Dec. 28, 2012, 6:47 a.m. EST By Barbara Kollmeyer, MarketWatch MADRID (MarketWatch) — U.S. stock-market futures fell on Friday ahead of the Chicago purchasing-managers index and pending-home-sales data, and before a key meeting between President Barack Obama and congressional leaders as they make a last-ditch effort to avert the fiscal cliff. Extending earlier losses, futures for…