Cannon Air Force Base, threatened with closure after its three F-16 fighter squadrons were ordered elsewhere, will become a special operations base, the Pentagon announced today. The base will become the Air Force's 16th Special Operations Wing within the next two years, Sen. Pete Domenici, R-N.M., said. ''It will change rather dramatically in character,'' he said. The base will have several different kinds of airplanes and more of them, Domenici and Gov. Bill Richardson said. ''It means the new focus of the special operations wing is the war on terrorism,'' Richardson said. ''The best news is that it looks like...