By Tom Westbrook and Xie Yu SINGAPORE/HONG KONG, Feb 22 (Reuters) - Global stocks tumbled while safe-havens rallied and oil surged on Tuesday as Europe's eastern flank stood on the brink of war after Russian President Vladimir Putin ordered troops into breakaway regions of eastern Ukraine. MSCI's broadest index of Asia Pacific shares outside Japan was on course for its worst day for this month, off 2.1%,...
