* Move /etc/gtk-3.0 to libgtk-3-common.
* Add appropriate Breaks/Replaces to handle it.
* Remove gtk-query-immodules-3.0 from libgtk-3-bin since it is
clearly not Multi-Arch compatible. It should not be needed anyway,
everything is handled by triggers from the private directory.
* Remove incorrect M-A: same statement for the debug package.