cont: Three more functions for GTree

[Svanberg Liss <lisss ydab se>]

> Hello!
> Is there any interest to include these extensions to GTree in glib-1.3?

Sorry, I forgot the diff...
It's created against glib in the cvs, using "cvs diff glib".
( Is this the correct way of creating a diff? )

I would really apprieciate if you told me whether or not you accept this
patch, because I need this functionality (quickly lookup a -range- of
values). If you doesn't want it in glib, then I'll have to put it in a
library of my own.

// Liss

glib.diff