Reuters: U.S. Republicans called on Monday for an end to a controversial requirement that gasoline contain a set amount of ethanol, a policy backed by the Bush administration that critics say has helped drive up world food prices. In their 2008 platform detailing policy positions, Republicans said markets — not government — should determine how much ethanol is blended into gasoline, and pushed for development of a cellulosic version, which could be made from grasses rather than …