[gtk] (12 commits) ...Merge branch 'matthiasc/for-master' into 'master'

[Matthias Clasen <matthiasc src gnome org>]

Summary of changes:

  ecaf6fc... docs: Add GtkTreeExpander (*)
  a8d433d... docs: Link to GtkTreeRowReference (*)
  adf0e8b... docs: Fix examples (*)
  5f33f4a... docs: Add an example (*)
  b9e8935... docs: Document GtkBitsetIter (*)
  8f7c207... docs: Add more GtkExpression (*)
  5e97df5... bitset: try again (*)
  72d66df... docs: Revise sorter docs a bit (*)
  bcd650f... docs: Revise the filter docs a bit (*)
  353d4d1... Cosmetic docs change (*)
  ec10857... docs: Move columns below columnview (*)
  9742200... Merge branch 'matthiasc/for-master' into 'master'

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