These are not used currently. Just put them in now in case we need them in the future.
_-prefix most of the get_type functions in a11y/. There are still some more symbols left.
At the same time, drop the AtkText implementation. Also, reintroduce a GtkBoxAccessible, since the previous way of setting the role in get_accessible was affecting GtkBox subclasses negatively. Adjust expected test output to match.
