SINGAPORE/LONDON (Reuters) - Oil prices fell on Monday on concerns about slackening global demand that outweighed bullish signals from Europe, where fears of an economically damaging no-deal Brexit have eased.Global benchmark Brent crude oil was down 30 cents to $59.12 a barrel by 0905 GMT. U.S. West Texas Intermediate crude oil declined 11 cents to $53.67 a barrel.Signs of still ample global oil supplies, combined with concerns about economic growth in China, the world's largest oil importer,..