[mutter] (16 commits) ...wayland: Drop -terminate argument to Xwayland

[Jonas Ådahl <jadahl src gnome org>]

Summary of changes:

  0200f4f... x11: Move focus sentinel to MetaX11Display (*)
  39bac6e... core: Turn MetaStack into a GObject (*)
  ef074ea... x11: Add MetaX11Stack object (*)
  103c469... core: Avoid grab transfer shenanigans with non-X11 backend (*)
  dbe6e01... core: Separate checks for pointer barriers availability (*)
  5e0523c... x11: Move X11 calls to map/unmap a MetaWindow to MetaWindow (*)
  2f21710... core: Relax requirement that MetaWindow shall have icon/min (*)
  1d77641... x11: Separate X11 focus handling into MetaX11Display method (*)
  86de79c... core: Untangle input focus management (*)
  465e131... core: Add explicit init/shutdown_x11() MetaDisplay calls (*)
  7713006... x11: Unmanage X11 windows on MetaX11Display finalization (*)
  1cf4279... x11: Initialize GdkDisplay together with MetaX11Display (*)
  430f354... wayland: Split Xwayland initialization in 2 steps (*)
  38432da... compositor: Drop error trap (*)
  ea9d8a8... wayland: Drop error trap (*)
  b1ea768... wayland: Drop -terminate argument to Xwayland (*)

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