Crude futures give back gains made in the wake of the ouster of Venezuelan President Nicolas Maduro by the U.S., settling below their pre-weekend levels.If the U.S. were to lift sanctions on Venezuelan oil it could release barrels "and only add to the surplus that the market is already experiencing," says Mizuho's Robert Yawger.A substantial increase in Venezuelan production is widely expected to be a long-term prospect, although from around 1 million barrels a day at present "Venezuela could get to 1.5 mil ...