Nobody mentioned the approach taken in the following patch yet though..
I saw it pass on the debian-gtk-gnome mailinglist a couple of days ago:
http://members.chello.nl/~h.lai/gtkenhancements/
What is being done is just copying the needed structures to a header
file withing gtk+, and opening the libraries at run time if they exist.
While I agree it is an ugly hack, I DO think it's the best approach: we
don't introduce a (build-)dependency on gnome-vfs in gtk+ or vice versa,
and as an added bonus pure gtk+ apps can benefit from the extra functio-
nality without having to depend on libgnomeui (for the icons).
I think you get the best of both worlds this way, but I'm afraid it will
be shot down with the argument of "ugly hack" :/