GLOBAL MARKETS-Shares jump, yen slumps as BOJ cranks up stimulus

* BOJ surprises markets as it accelerates stimulus drive * Nikkei surges 4.8 pct to highest since Nov 2007, yen at 7-yr low * Euro zone inflation expected to keep pressure on ECB to ease * Rouble sheds some of Thursday's gains ahead of c.bank decision By Marc Jones LONDON, Oct 31 (Reuters) - World shares jumped and the yen fell to a seven-year low against the dollar on Friday as the Bank of Japan surprised financial markets by significantly expanding its massive stimulus pro