(Corrects 10th paragraph to show Monday's price gain for gold was nearly 1 percent, not 4 percent) * Gold marks biggest advance in months for a second day * Copper rises too after upbeat U.S. housing data * Oil down again on worries over Italian vote * Corn has sharpest rally in 6 weeks; sugar, cocoa tumble By Barani Krishnan NEW YORK, Feb 26 (Reuters) - Gold's biggest rally in months stretched into a second day on Tuesday after the U.S. Federal Reserve chief defended th