BOSTON — One of two men who helped carry a fellow runner across the finish line of the Boston Marathon said he had been struggling earlier himself but drew strength from the supportive crowd. "If I had to go farther, I would have," Aaron Beggs said in an interview on Thursday. "It's fight or flight, and I decided to fight and help him get to our destination." Beggs, of Northern Ireland, and Robson De Olivera, of Brazil, sprang into action Monday when Ajay Haridasse collapsed about 1,000 feet