Now, about gtk_tree's

["simon kendall" <malicious kendall gmail com>]

Hi,
So, following the advice of converting the lists to trees, I started
changing all the functions into tree-oriented ones. I have a book on
the subject, and I read the section on trees as there is no
documentation on gtk.org. Now, for every tree-related function I write
my compiler says it's undeclared. Also checked developer.gnome.org,
but that does not either say anything about such. Anything I'm doing
wrong, you think?