Use best known derived parent

Use best known derived parent

In the case where a known class derives from a hidden one, we want
to use the most-derived parent class, rather than simply falling back
to GObject.

Example:
ShellEmbedWidget in gnome-shell derives from ClutterGLXTexturePixmap from clutter,
which is a hidden class.  ClutterGLXTexturePixmap's parent itself is
ClutterX11TexturePixmap, which is also hidden.  But its parent is
ClutterTexture, which we do know.  Use that.

https://bugzilla.gnome.org/show_bug.cgi?id=598993