CANADA STOCKS-TSX little changed as investors await Yellen speech

* TSX down 5.86 points, or 0.04 percent, at 15,556.09 * Seven of 10 main index sectors decline * Goldcorp, Barrick slip with bullion price By John Tilak TORONTO, Aug 21 (Reuters) - Canada's main stock index was little changed on Thursday as investors awaited a speech from U.S. Federal Reserve Chair Janet Yellen to scan for clues about the central bank's outlook for interest rates. The market also processed figures showing a bigger-than-expected drop in the number of American