(LEAD) Carter in N. Korea to free imprisoned American amid brewing nuclear diplomacy By Sam Kim SEOUL, Aug. 25 (Yonhap) -- Former U.S. President Jimmy Carter arrived Wednesday in North Korea, official media reports said, as he sought to secure the release of an American imprisoned there amid brewing signs of diplomacy aimed at reviving nuclear talks involving Pyongyang. "Jimmy Carter, ex-president of the U.S., and his party arrived here Wednesday," the North's Korean Central News Agency said in a brief dispatch seen here, adding Pyongyang's top nuclear envoy, Kim Kye-gwan, received him at the airport. A child handed the...