message: Add config_value_map convenience alias
diff: @@ -158,6 +158,10 @@ private:
  variant_type data_;
  };
  +/// Organizes config values into categories.
  +/// @relates config_value
  +using config_value_map = std::map<std::string, config_value::dictionary>;
  +
  /// @relates config_value
  template <class T>
  struct config_value_access;
  @@ -453,8 +457,7 @@ std::string get_or(const config_value::dictionary& xs, const std::string& name,
  /// Tries to retrieve the value associated to `name` from `xs`.
  /// @relates config_value
  template <class T>
  -optional<T> get_if(const std::map<std::string, config_value::dictionary>* xs,
  - const std::string& name) {
  +optional<T> get_if(const config_value_map* xs, const std::string& name) {
  // Get the category.
  auto pos = name.find('.');
  if (pos == std::string::npos) {
  @@ -472,8 +475,7 @@ optional<T> get_if(const std::map<std::string, config_value::dictionary>* xs,
  /// Retrieves the value associated to `name` from `xs`.
  /// @relates config_value
  template <class T>
  -T get(const std::map<std::string, config_value::dictionary>& xs,
  - const std::string& name) {
  +T get(const config_value_map& xs, const std::string& name) {
  auto result = get_if<T>(&xs, name);
  if (result)
  return std::move(*result);
  @@ -484,8 +486,8 @@ T get(const std::map<std::string, config_value::dictionary>& xs,
  /// `default_value`.
  /// @relates config_value
  template <class T, class E = detail::enable_if_t<!std::is_pointer<T>::value>>
  -T get_or(const std::map<std::string, config_value::dictionary>& xs,
  - const std::string& name, const T& default_value) {
  +T get_or(const config_value_map& xs, const std::string& name,
  + const T& default_value) {
  auto result = get_if<T>(&xs, name);
  if (result)
  return std::move(*result);
  @@ -495,8 +497,8 @@ T get_or(const std::map<std::string, config_value::dictionary>& xs,
  /// Retrieves the value associated to `name` from `xs` or returns
  /// `default_value`.
  /// @relates config_value
  -std::string get_or(const std::map<std::string, config_value::dictionary>& xs,
  - const std::string& name, const char* default_value);
  +std::string get_or(const config_value_map& xs, const std::string& name,
  + const char* default_value);
  /// Tries to retrieve the value associated to `name` from `cfg`.
  /// @relates config_value
  