Stocks turned in a lackluster performance throughout much of the session on Wednesday before seeing substantial volatility in afternoon trading following the Federal Reserve's highly anticipated monetary policy announcement.The major averages showed wild swings back and forth across the unchanged line before eventually closing mixed. While the Dow climbed 260.42 points or 0.6 percent to 46,018.32, the S&P 500 edged down 6.41 points or 0.1 percent to 6,600.35 and the Nasdaq fell 72.63 points or 0.3 percent ...