* TSX falls 7.83 points or 0.06 percent, to 12,781.19 * Barrick Gold down after African unit disappoints * Thomson Reuters shares slip after results * Talisman up nearly 2 percent after posting profit By John Tilak TORONTO, Feb 13 (Reuters) - Canada's main stock index edged lower on Wednesday, led by a decline in Barrick Gold Corp , the world's largest gold producer, after the release of disappointing earnings from the its African subsidiary. A 3.1-percent drop in shares