message: Fix build on Clang 3.6
diff: @@ -361,12 +361,19 @@ T get(const actor_system_config& cfg, string_view name) {
  /// Retrieves the value associated to `name` from `cfg` or returns
  /// `default_value`.
  /// @relates config_value
  -template <class K, class V>
  -auto get_or(const actor_system_config& cfg, K&& name, V&& default_value)
  - -> decltype(get_or(content(cfg), std::forward<K>(name),
  - std::forward<V>(default_value))) {
  - return get_or(content(cfg), std::forward<K>(name),
  - std::forward<V>(default_value));
  +template <class T, class = typename std::enable_if<
  + !std::is_pointer<T>::value
  + && !std::is_convertible<T, string_view>::value>::type>
  +T get_or(const actor_system_config& cfg, string_view name, T default_value) {
  + return get_or(content(cfg), name, std::move(default_value));
  +}
  +
  +/// Retrieves the value associated to `name` from `cfg` or returns
  +/// `default_value`.
  +/// @relates config_value
  +inline std::string get_or(const actor_system_config& cfg, string_view name,
  + string_view default_value) {
  + return get_or(content(cfg), name, default_value);
  }
  } // namespace caf
  