By LESLIE JOSEPHS  December 12, 2012, 3:33 p.m. ET NEW YORK—A surprise increase in sugar output from top producer Brazil sent futures prices for the sweetener down to a 28-month low. Raw sugar for March delivery on ICE Futures U.S. dropped 1.8% to settle at 18.54 cents a pound, the lowest settlement since Aug. 11, 2010….