codegen::sys::lib: Generalize fn prepare
codegen::sys::lib: Generalize fn prepare

GuillaumeGomez/gir,EPashkin/gir,gtk-rs/gir,gkoz/gir,EPashkin/gir,gkoz/gir,insanebits/gir,insanebits/gir,gtk-rs/gir,GuillaumeGomez/gir,GuillaumeGomez/gir,gtk-rs/gir