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

[Matthias Clasen <matthiasc src gnome org>]

Summary of changes:

  9156be6... viewport: Drop the Private struct (*)
  2ea7f47... separator: Drop the Private struct (*)
  7ede3b9... calendar: Drop the Private struct (*)
  a78e0f1... fontchooserwidget: Drop the Private struct (*)
  5bd2b49... fontchooserdialog: Drop the Private struct (*)
  bf77694... linkbutton: Drop the Private struct (*)
  2356c9b... overlay: Drop the Private struct (*)
  508ed21... progressbar: Drop the Private struct (*)
  dc99a7a... stackswitcher: Drop the Private struct (*)
  7da995d... Merge branch 'matthiasc/for-master' into 'master'

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