By Hyonhee Shin and Josh Smith SEOUL (Reuters) – North Korea is shaking up the way it handles relations with South Korea, enacting changes to policy and government organisations that would effectively treat the South as a separate, enemy state. The moves, which break with decades of policy, could have North Korea’s foreign ministry taking over relations with the South, and potentially help justify the use of nuclear weapons against Seoul in a future war, analysts said. Since the 1950-53 Korean War ended in a stalemate, both nations have had policies that treat each other differently than other…