A DC-10 WAS ENTERING ITS FINAL LANDING APPROACH AT J.F.K. recently when it suddenly banked wildly to the left, nearly causing a crash before the crew got things under control. Seems that the airliner's electronic flight controls went wacky when somebody in first class turned on his portable CD player. Experts at NASA, the National Transportation Safety Board and the Federal Aviation Administration have concluded that stray electronic emissions from CD players, cellular phones, radios, electronic games and even portable computers can interfere with flight controls during takeoffs and landings. New, more sternly worded warnings may be in the offing.