Consider nullability overrides for out parameters too
Consider nullability overrides for out parameters too

This just adds to an existing hack. The code analyzing out parameters
has to be completely rewritten based on the analyzed parameters instead
of the library (XML) ones.

GuillaumeGomez/gir,GuillaumeGomez/gir,gtk-rs/gir,gtk-rs/gir,GuillaumeGomez/gir,gtk-rs/gir