KUALA LUMPUR, Malaysia — Malaysia performed a second autopsy on the estranged half brother of North Korea’s leader because the first procedure was inconclusive, piling on the intrigue surrounding what appeared to be a well-executed assassination at an airport in Kuala Lumpur, an official said Saturday. Police arrested a fourth suspect, identified as a North Korean man. The second autopsy clearly enraged North Korea, which has vowed to reject the results of any post-mortem and demanded that Malaysia turn over the body immediately.