NEW YORK, June 26 (Reuters) - Boeing Co. (BA.N: Quote, Profile , Research) on Tuesday named retired Marine Corps Gen. James Jones, the former head of U.S. and NATO forces in Europe, to its board. The appointment is the latest in a line of retired senior armed forces and Pentagon leaders joining defense contractors, underscoring the tight relationship between U.S. arms makers and buyers. Boeing, which is the No. 2 U.S. defense contractor behind Lockheed Martin Corp. (LMT.N: Quote, Profile , Research), said Jones' appointment was effective immediately. Jones, 63, is a decorated Vietnam War veteran with a 40-year military...