[gtk] (10 commits) ...Merge branch 'wip/otte/for-master' into 'master'

[Benjamin Otte <otte src gnome org>]

Summary of changes:

  9a2f4d8... fontbutton: Make sure the window is on the same display (*)
  480112f... fontbutton: Destroy dialog in unrealize() (*)
  552b71d... stylecontext: Remove unneeded headers (*)
  1957915... rendernode: Add GValue functions for render nodes (*)
  0b7a36c... rendernode: Add (de)serialization support for render nodes (*)
  18affbd... dragicon: Add a default drag icon for GskRenderNode (*)
  cbc050b... recorder: Make the render nodes in the list draggable (*)
  2863095... node-editor: Allow dragging and dropping the center picture (*)
  119458f... contentdeserializer: Fix some API awkwardness (*)
  32899a1... Merge branch 'wip/otte/for-master' into 'master'

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