-Update to 5.6.0.
* Fix some introspection problems.
* Use github instead of circleci.
* Keybindings: Add a default keybinding for 'switch-panels-backward'.
* gvc-channel-map.c: Fix return with a value in a void function.
* gnome-wall-clock.c: Fix a gi scanner warning.
* fix a null pointer deref scan-build found.
* Add a setting for notification duration.
* Removed fix_return_value_void.patch as it's no longer needed.