[gtkada] Compile error in GtkAda 2.0.0

[Arnaud Charlet]

> One file didn't compile because of what looked like a gnat bug.
> I'm using gnat 3.12. It complained: No selector "" for [...]
> when it encountered a use of a renamed subprogram.
> It was easily solved though by avoiding the deprecated names.
> The file in question is gtkada-mdi.adb. This is the diff:

We need contextual (-c) or unified (-u) patches, and the
other way around: old first, new next, otherwise it is not practical
to review them, thanks.

Arno