[gtk] (6 commits) Non-fast-forward update to branch wip/matthiasc/focus2

[Matthias Clasen <matthiasc src gnome org>]

The branch 'wip/matthiasc/focus2' 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:

  b328ed0... Port widget to the root focus API

Commits added to the branch:

  9270dbe... Port widgets to the root focus API
  cdbddfa... Move a check to gtk_window_set_focus
  f07be15... Simplify the move_focus api
  d3f94c5... widget: Drop the ::focus signal
  d3771c5... widget: Add a next-focus-child API
  8ecfab4... stack: Implement next_focus_child