[gtk] (9 commits) ...Merge branch 'matthiasc/for-master' into 'master'

[Matthias Clasen <matthiasc src gnome org>]

Summary of changes:

  c8b5715... bitset: Correct preconditions in gtk_bitset_add_rectangle (*)
  c4e8218... bitset: Add more tests (*)
  b77110c... bitset: Fix documentation syntax (*)
  cab6808... gtk-demo: Fix binary name in --version (*)
  4f7f157... node-editor: Document the node format (*)
  8770584... node-editor: Add a gear menu (*)
  2b6f243... node-editor: Cosmetics (*)
  d4ff275... node-editor: Add a help window (*)
  6ddd979... Merge branch 'matthiasc/for-master' into 'master'

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