[gtk+] Non-fast-forward update to branch wip/baedert/children

[Timm Bäder <baedert src gnome org>]

The branch 'wip/baedert/children' was changed in a way that was not a fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  20405c9... widget: Warn on destroy if not all child widgets have bee d

Commits added to the branch:

  5138808... widget: Warn if children are left in finalize()