text: Wal-Mart Sales Slump Keeps Stocks Muddled NEW YORK - Wal-Mart Stores Inc.'s disappointing sales forecast sent stocks fluctuating Monday as investors' concerns about a slowing economy eclipsed their relief over a drop in oil prices.    October contracts for a barrel of light crude were quoted at \$46.25, down 47 cents, on the New York Mercantile Exchange...