GLOBAL MARKETS-Equities extend rally; oil rebounds, helping rouble rise

(Updates prices, quote) * European shares after 3-day rally * Rouble bounces over 3 percent, oil above $60 a barrel By David Gaffen NEW YORK, Dec 19 (Reuters) - Equity markets worldwide extended the week's rally on Friday and oil prices rebounded from recent lows, even though market volumes were beginning to thin as investors started to reduce exposure as the end of year approaches, traders said. Wall Street posted modest gains after the S&P 500's best two-day rally in three