GLOBAL MARKETS-Stocks climb on Fed policy signals; oil slips again

(Updates with Wall Street rally, latest prices; changes dateline; previous LONDON)* Wall Street on track for second day of strong gains* Shares jump as Fed pledges to be patient on withdrawing stimulus* Oil down after brief short-covering gainsBy Michael ConnorNEW YORK, Dec 18 (Reuters) - Global equities markets rallied on Thursday, with Wall Street up more than 1 percent for a second straight day