NEW YORK (CNNMoney.com) -- U.S. stock markets posted slight gains at the start of a busy Wednesday, after a big Republican victory in the midterm election and ahead of a key Federal Reserve meeting. The Dow Jones industrial average (INDU) added 26 points, or 0.2%, and the S&P 500 (SPX) gained 2 points, or 0.2%. The tech-heavy Nasdaq (COMP) rose 2 points, or 0.1%. Stocks closed higher Tuesday after interest rate hikes from the central banks of Australia and India sparked an early rally. But the market traded in a narrow range for most of the day as investors remained...