Futures flat ahead of U.S. Fed minutes

August 17 (Reuters) - Stock futures pointed to a lower opening for Canada's main stock index on Wednesday as investors await the minutes of the U.S. Federal Reserve's July policy meeting for clues on the next interest rate hike. The Fed is raising expectations for an interest rate rise this year, even as early as next month, despite weak U.S. economic growth in the first half of 2016. Oil prices slipped for the first time in a week as investors weighed the success of potential talks among top oi