[mutter] (15 commits) Non-fast-forward update to branch wip/tintou/background-class-derivable

[Corentin Noël <corentinnoel src gnome org>]

The branch 'wip/tintou/background-class-derivable' 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:

  4039723... meta: Make MetaBackgroundGroup derivable

Commits added to the branch:

  181c7ca... wayland: Use right sign for workspace ID (*)
  c35e561... xwayland: Use g_get_host_name instead of gethostname (*)
  0185909... window-x11: Fix _XOPEN_SOURCE usage for gethostname on Free (*)
  6055f04... display: Remove _XOPEN_SOURCE definition (*)
  eccc791... workspace: Focus only ancestors that are focusable (*)
  e1f839f... tests: Add 'accept_focus' command to runner and client (*)
  f2d2d47... tests: Add 'can_take_focus' command to runner and client (*)
  2fc7760... tests, stacking: Add tests with no-input and no-take-focus  (*)
  51f9e04... test-runner: Add 'assert_focused' command (*)
  fcb408a... tests: Verify focused window in closed-transient tests (*)
  d08763c... test-runner: Add 'sleep' command (*)
  6022b23... test-runner: Add 'dispatch' command (*)
  f71151a... window-x11: Focus the default window with delay while waiti (*)
  e14613e... window: Warn if try to focus unmanaging windows (*)
  9335189... meta: Make MetaBackgroundGroup derivable

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