message: fix stl file format
  * fix stl file format
  * Update io_stl.hpp
  typo
diff: @@ -60,6 +60,7 @@ namespace
  void end_triangle( std::ostream& out )
  {
  out << "endloop" << EOL;
  + out << "endfacet" << EOL;
  }
  void save_triangle_vertex( const GeoModel3D& geomodel,
  