[gtk] (18 commits) ...Merge branch 'window-destroy' into 'master'

[Matthias Clasen <matthiasc src gnome org>]

Summary of changes:

  8f9c3ed... Stop using gtk_widget_destroyed (*)
  573b20a... Drop gtk_widget_destroyed (*)
  b6bfeb7... fontchooserdialog: Fix disposing (*)
  4b14485... colorchooserdialog: Fix disposing (*)
  0ba1aad... filechooserdialog: Fix disposing (*)
  ddebf07... popover: Fix a reference leak (*)
  466d2a8... testsuite: Clean up unexpected children (*)
  81340da... nativedialog: Do not ref the transient_for parent (*)
  48821a6... window: Add gtk_window_destroy (*)
  cd0081d... Use gtk_window_destroy (*)
  025375f... Replace gtk_widget_destroy everywhere (*)
  6aebedb... window: Implement gtk_window_destroy (*)
  0f10b17... widget: Drop gtk_widget_destroy (*)
  e5d6b49... testsuite: add widget refcount test case (*)
  1306727... window: Remove _set_has_user_ref_count (*)
  177c0eb... Unset tooltip window earlier (*)
  6d969d1... Update the docs (*)
  7ae1d9d... Merge branch 'window-destroy' into 'master'

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