U.S. SAYS SUSPECTS AWAITED AN ORDER FOR TERROR STRIKE
Federal officials say five Arab-American arrested in Lakawanna, NY, on Sept 13 received intensive weapons training in Afghanistan in summer of 2001 and were sent back to US to await order for attack; men, all born in US and of Yemeni descent, are charged with providing 'material support' to Al Qaeda by attending training camp, same one that John Walker Lindh attended; Lindh's lawyer declines to say whether he directed investigators to alleged cell; friends and relatives rally to defense of suspects, many suggesting that arrests are result of anti-Muslim witchhunt; photos (M)