Parameter key in Gio::Settings::writable-change-event signal should be of type GQuark, not guint. However, my patch doesn't break the API, because:

typedef guint32 GQuark;
typedef unsigned int guint32;
typedef unsigned int guint;

Please review. If no objections, I'll push it.

Btw, I've discovered this bug writing new mm .defs generator based on gobject-introspection (in the future I think it could generate more advanced output, like .hg/ccg or something else)[1]. Still a lot of work before it can be replacement for our current python/perl/c++ programs for generating defs file, but I think it goes in right direction.

[1] https://github.com/loganek/mmgirgenerator