[gtk] (6 commits) Non-fast-forward update to branch wip/otte/guadec2018

[Benjamin Otte <otte src gnome org>]

The branch 'wip/otte/guadec2018' 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:

  53e3428... gtk: Add GtkZoom
  0ed2c3a... mediafile: Export gtk_media_file_get_impl_type()
  49138f2... demos: Add GTK4 lightning talks talk
  34f99a6... paintable: Fix return_if_fail() statements
  a2c61e6... xxx: talk
  f765d86... widgetpaintable: Redo implementation
  4bd3b0b... xxx: talk
  2de1586... widgetpaintable: Add a hack to make recursion not infloop

Commits added to the branch:

  50496fc... paintable: Fix return_if_fail() statements
  31c3a76... gtk: Add GtkZoom
  100be54... mediafile: Export gtk_media_file_get_impl_type()
  4865635... demos: Add GTK4 lightning talks talk
  436bda7... widgetpaintable: Redo implementation
  a089de7... widgetpaintable: Add a hack to make recursion not infloop