message: Change ListBoxBase::ListBoxItem from class to struct
  All members are public anyway.
diff: @@ -34,9 +34,8 @@ public:
  * Derived SpecialListBox types can inherit from this struct
  * for specialized information needed for derived types.
  */
  - class ListBoxItem
  + struct ListBoxItem
  {
  - public:
  ListBoxItem() = default;
  ListBoxItem(std::string text) : Text(text) {}
  virtual ~ListBoxItem() = default;
  