message: mark CoXHash::key_for_idx as const
diff: @@ -142,7 +142,7 @@ public:
  in_use++;
  return &m_storage[entry_idx];
  }
  - KEY *key_for_idx(int idx)
  + const KEY *key_for_idx(int idx) const
  {
  idx-=1;
  if(idx >= 0 && idx < (int)m_storage.size())
  