By R.J. Young MOORE, Oklahoma (Reuters) - A massive tornado tore through the Oklahoma City suburb of Moore on Monday, killing at least 51 people with winds of up to 200 miles per hour that flattened entire tracts of homes, two schools and a hospital, leaving a wake of tangled wreckage. Rescue workers raced against the setting sun to find survivors in Oklahoma as the dangerous storm system threatened as many as 10 U.S. states with more twisters. The Oklahoma medical examiner confirmed 51 deaths, making it the deadliest U.S. ...