Version requirements for Xfce 4.4

[Nick Schermer]

Well the next 2 weeks I'm reviewing the entire test website, so it's
ready when 4.4 is released and the requirements page certainly needs
some more work.

> For consistency's sake, I'd say just mark all the gtk/glib version
> requirements at 2.6.0 minimum (except for those that require 2.6.4).
> It's just easier that way, and I know those aren't quite correct
> (xfdesktop requires at *least* 2.4 [maybe 2.6], though you have 2.2 in
> the list).  At any rate, our configure.ac files should all specify 2.6.x.
>

I'll change that, tnx.

Nick