[gtk+] (14 commits) ...gtkdnd: Hardcode the DnD window onto the drag widget window on Wayland

[Carlos Garnacho <carlosg src gnome org>]

Summary of changes:

  9c16d8b... gdk: Add GDK_DRAG_PROTO_WAYLAND (*)
  5fcf2de... gdk: Remove check for source window (*)
  bd41042... gtkselection: Ensure the X11 specific message length only a (*)
  32bf03c... wayland: implement text_property_to_utf8_list() (*)
  3b95304... wayland: Implement drop/destination side of selections (*)
  7744799... wayland: Implement drag/source side of selections (*)
  f48b3cc... wayland: Replace clipboard implementation (*)
  9b0b88d... wayland: Implement the dropping part of DnD (*)
  7b85a34... wayland: Implement drag sources (*)
  867302e... wayland: Don't set an xdg surface to DnD windows (*)
  6ba7d34... wayland: Return properly type hints from GdkWindows (*)
  8504890... wayland: Add private API to retrieve the drag window for a  (*)
  ee93db1... window: Add private API to hardcode the main GdkWindow for  (*)
  14b4e4d... gtkdnd: Hardcode the DnD window onto the drag widget window

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