[gtk] (21 commits) Non-fast-forward update to branch headless-seatless

[Matthias Clasen <matthiasc src gnome org>]

The branch 'headless-seatless' 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:

  fe81bd1... gtk: Handle seatless displays
  424d8ba... docs: Clarify gdk_display_get_default_seat() docs
  60d7003... ci: Add weston and weston-libs to the fedora image
  17f3e2b... ci: Fix a typo in the run-docker.sh script
  269fea9... tests: Allow setting a subdir for output
  154db66... testsuite: Add test setups for backends
  c4e185c... ci: Run tests with different backends

Commits added to the branch:

  5dc6194... eventcontrollerscroll: Fix the history push condition (*)
  3df0f95... Merge branch 'wip/exalm/kinetic_scrolling' into 'master' (*)
  aadd9ae... tests: Drop testbuttons (*)
  52c630d... tests: Drop testgiconpixbuf (*)
  dca142d... tests: Drop testemblems (*)
  4079b78... tests: Drop testorientable (*)
  1e2b5a9... tests: Consolidate all headerbar tests (*)
  9e8d845... tests: Rename testheaderbar2 to testheaderbar (*)
  dcfb469... tests: Drop testdnd3 (*)
  acae90c... Merge branch 'tests-cleanup' into 'master' (*)
  d7e6fbf... Adwaita: notebook tab focus tweak (*)
  b51a544... Merge branch 'wip/jimmac/tabs-again-focus' into 'master' (*)
  80473cc... widget: Add array annotation to set_css_classes (*)
  d4d9644... Merge branch 'wip/tintou/set_css_classes_array' into 'maste (*)
  6fa6443... gtk: Handle seatless displays
  a5def45... docs: Clarify gdk_display_get_default_seat() docs
  aa8c7ee... ci: Add weston and weston-libs to the fedora image
  4f55c01... ci: Fix a typo in the run-docker.sh script
  ed300d1... tests: Allow setting a subdir for output
  2b6735e... testsuite: Add test setups for backends
  cb6c7b3... ci: Run tests with different backends

(*) This commit already existed in another branch; no separate mail sent