Automatically add support for the new cleanup macros to the type
declaration macros.
This is an API break because now your parent class needs to support
cleanup if you want to use G_DECLARE_*_TYPE. These macros are only 1
day old, however, so that's probably not a big problem (and we are
already busy adding the macros all over GLib and Gtk+).
https://bugzilla.gnome.org/show_bug.cgi?id=743640