NEW YORK (Reuters) - U.S. airport baggage screeners, displaying seized chain saws, machetes and knives, warned travelers to check their luggage for offensive objects before boarding a flight. Officials of the Transport Security Administration, speaking ahead of this weekend's Labor Day holiday -- a busy travel time -- said that since February 2002 more than 7.5 million prohibited items had been seized. They included 50,000 box cutters -- a weapon said to be used by the Sept. 11, 2001 hijackers -- and 1,437 firearms as well as 2.3 million knives. The TSA officials told a news conference most people with...