CORSICAN NATIONALISTS set off bombs Thursday across the Mediterranean Island, destroying 48 homes in a vacation colony and briefly holding 16 hostages in two other assaults, authorities said. . . . POWERFUL COCAINE BARONS have slain four policemen in Medellin, Colombia, police said, in what may signal the resumption of the drug traffickers' war against the government. . . . A TEAM OF U.S. specialists is visiting Hanoi to seek Vietnamese government documents and historical data to help account for the 2,288 Americans still listed as missing in action in Southeast Asia. . . . AT LEAST 322 people died on the nation's highways during the long New Year's Day weekend, the National Safety Council says.