CANADA STOCKS-TSX weakens modestly as commodity prices drop

By Leah Schnurr TORONTO, Sept 8 (Reuters) - Canada's main stock index edged lower on Monday as weaker commodities prices, including oil's drop below $100 a barrel, weighed on shares of energy and mining companies. Gains in Canadian National Railway and Canadian Pacific Railway after Goldman Sachs raised its share-price targets for the two companies helped mitigate the market's losses. The railway shares were among the index's biggest gainers. CN Rail was up 0.9 percent at C$80.63, an