GLOBAL MARKETS-Shares, dollar steady ahead of key U.S. data, Fed meeting

(Updates with U.S. market close) * Russia stocks tumble again after new sanctions * Investors hesitant to make bets ahead of U.S. GDP, payrolls data * Fed expected to maintain dovish tone on Wednesday By Angela Moon NEW YORK, July 28 (Reuters) - World stock markets were little changed on Monday while the U.S. dollar traded mostly flat against a basket of major currencies ahead of key U.S. economic reports and events this week. Wall Street ended flat as the latest deal ne