[Vala] Iterator for GLib.List?

[JM <interflug1 gmx net>]

Hello

GLib.List<T> can be used with foreach(T t in list) in vala. This is
possible even without having an Iterator iterator(). So it looks like
this is not coming from methods with syntax support as mentioned in the
tutorial.
Is there some special code for GLib.List in vala and if so, is there a
possibility to use it for custom code (like for a node like object that
has children chained to each other like in a double-linked list)? 

Regards
Jörn