message: das.printer: Fix warnings in test suite.
diff: @@ -16,6 +16,7 @@ struct NoModel
  int foo, bar;
  };
  +static
  void
  no_model()
  {
  @@ -31,6 +32,7 @@ struct BuiltinModel
  elle::das::Model<BuiltinModel, elle::meta::List<Symbol_foo, Symbol_bar>>;
  };
  +static
  void
  builtin_model()
  {
  @@ -47,6 +49,7 @@ ELLE_DAS_MODEL_DEFAULT(
  ExternalModel,
  (elle::das::Model<ExternalModel, elle::meta::List<Symbol_foo, Symbol_bar>>));
  +static
  void
  external_model()
  {
  