(Reuters) - Britain's Serious Fraud Office (SFO) has launched an investigation into Glencore over suspicions of bribery, it said on Thursday, adding to the legal woes of one of the world's biggest commodity traders.Since July last year, Glencore has been subject to a U.S. Department of Justice enquiry in connection with corruption in the Democratic Republic of Congo, Venezuela and Nigeria.Britain's SFO on Thursday said it was also investigating the conduct of Glencore businesses, its officials,..