Bug 621076 - GtkTreeModelFilter does not emit all signals in some ...
The bulk of the fix is to walk the chain of ancestors, starting at the
root level, and check if the visibility of any of the ancestors has
changed. If yes, the necessary signals are emitted so that this change
is propagated properly. This walk is done after a node has been
inserted, changed or deleted, see function
gtk_tree_model_filter_check_ancestors().
Bug reported, and initial debugging and analysis, by Xavier Claessens.