[gtk] (4 commits) Non-fast-forward update to branch wip/chergert/action-parent

[Christian Hergert <chergert src gnome org>]

The branch 'wip/chergert/action-parent' 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:

  b29df12... widget: add gtk_widget_set_action_parent()
  158fd75... actionmuxer: set handler ids initially to zero
  dda5ce2... actionmuxer: check for observer before unregistering
  c0057f3... actionmuxer: add test for action parent

Commits added to the branch:

  25937d2... widget: add gtk_widget_set_action_parent()
  f2a812b... actionmuxer: set handler ids initially to zero
  5988af7... actionmuxer: check for observer before unregistering
  4a38aba... actionmuxer: add test for action parent