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

[Matthias Clasen <matthiasc src gnome org>]

Summary of changes:

  bc2c341... gtk-demo: Visual fixes to the model button demo (*)
  ba25e08... menubutton: Add a use-underline property (*)
  163aa82... gtk-demo: Use mnemonics in menu buttons (*)
  059917b... gtk-demo: Fix the overlay demo (*)
  fbed55d... gtk-demo: Fix the rotated text demo (*)
  48910a6... gtk-demo: Fix the shortcuts demo (*)
  e2c327e... gtk-demo: Fix the sliding puzzle (*)
  f3d061e... gtk-demo: Fix the stack demo (*)
  858997d... Merge branch 'matthiasc/for-master' into 'master'

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