HEREWARD HOLLAND CONGO Republic President Denis Sassou Nguesso looks set to prolong his decades-long rule in an election on Sunday in which he has pledged to revive the flagging economy. Sassou, a 77-year old former paratrooper, rose to power in the oil-producing country on the western coast of central Africa in a military coup in 1979. He lost Congo's first multi-party elections in 1992 but regained power in 1997 after a civil war and has now ruled for a combined total of almost 37 years. Sassou will face six opposition candidates in an election whose run-up has been tightly controlled…