GLOBAL MARKETS-Yen plunges vs dollar, yen; Wall St steps back

* Dollar, euro leap vs yen on Brainard comments * Wall Street wans as it consolidates after recent highs * Euro currency war talk continues * U.S. crude jumps, though brent falters By Leah Schnurr NEW YORK, Feb 11 (Reuters) - The yen slid sharply against the dollar and the euro on Monday after a U.S. Treasury official voiced support for Japan's efforts to boost growth and end deflation. Wall Street and world equity markets were little changed in light volume as a lack o