message: Use Tile::xyz() in serializeStructure
diff: @@ -32,12 +32,12 @@ namespace
  NAS2D::Xml::XmlElement* serializeStructure(Structure* structure, Tile* tile)
  {
  - const auto position = tile->xy();
  + const auto position = tile->xyz();
  NAS2D::Dictionary dictionary =
  {{
  - {"x", position.x},
  - {"y", position.y},
  - {"depth", tile->depth()},
  + {"x", position.xy.x},
  + {"y", position.xy.y},
  + {"depth", position.z},
  }};
  dictionary += structure->getDataDict();
  