[gtk] (12 commits) ...Merge branch 'a11y/atcontext-realize' into 'master'

[Matthias Clasen <matthiasc src gnome org>]

Summary of changes:

  30210c7... a11y: Move ATContext to an explicit realization model (*)
  dafb2b0... a11y: Allow updating role on unrealized contexts (*)
  bb24b35... gtk-demo: Set an accessible role (*)
  828a067... Propagate accessible-role to backend (*)
  ae9758b... a11y: Unrealize ATContext on dispose (*)
  425d8ad... Set accessible label on GTK Demo's primary menu (*)
  d88f7c9... a11y: Use the tooltip text as the accessible description (*)
  72415ea... a11y: Make the Button labelled by its child label (*)
  ba63aa7... a11y: Move parent context ref getter to its own function (*)
  f220a1e... gtk-demo: Set some accessible properties (*)
  d2a7ecf... gtk-demo: Simplify the run button (*)
  23c4256... Merge branch 'a11y/atcontext-realize' into 'master'

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