* Corn close to flat after hitting lowest since Aug 2010 * Egypt deal supports wheat; no U.S. supply in purchase * Soybeans trading below 200-day moving average (Updates with U.S. trading, adds new analyst quote, dateline, byline) By Mark Weinraub CHICAGO, Nov 19 (Reuters) - U.S. soybean futures dropped 1.2 percent on Tuesday, pressured