DirichletBC.markers() wrong return value

[Felix Ospald]

const std::vector<std::pair<std::size_t, std::size_t> >& DirichletBC::markers() const
{
  return facets;
}

should be

const std::vector<std::pair<std::size_t, std::size_t> >& DirichletBC::markers() const
{
  init_facets();
  return facets;
}

otherwise the array may be empty in some cases...
Also in

void DirichletBC::init_facets() const
{
  Timer timer("DirichletBC init facets");

  if (facets.size() > 0)
    return;

  if (_user_sub_domain)
    init_from_sub_domain(_user_sub_domain);
  else if (_user_mesh_function)
    init_from_mesh_function(*_user_mesh_function, _user_sub_domain_marker);
  else
    init_from_mesh(_user_sub_domain_marker);
}

it may be better to put the Timer after the if (facets.size() > 0) return; statement.