* Glencore slides 30 percent, underscores commodity concern * Copper drops back under $5,000 a tonne * Fed's Dudley says rate hike could come in October (Updates with close of U.S. markets, oil settlement prices) By Chuck Mikolajczak NEW YORK, Sept 28 (Reuters) - Global equity markets and commodities slumped on Monday, pulled lower by worry over the economic health of China and other big emerging markets in a week filled with key economic data. An 8.8 percent drop in Chines
