Fix GList corruption when unsetting parent node

From: Daniel Drake <d.drake@mmm.com>

g_list_remove modifies the list, so the GObject data must be updated after the
remove

Index: papi-0.0.2/src/papi_atkobject.c
===================================================================
--- papi-0.0.2.orig/src/papi_atkobject.c
+++ papi-0.0.2/src/papi_atkobject.c
@@ -431,6 +431,7 @@ _atkobject_set_parent (PyAtkObject *self
             data = g_object_get_data (G_OBJECT (parent), PAPI_CHILDREN);
             data = g_list_remove (data, self->obj);
             ATKOBJECT (self)->accessible_parent = NULL;
+            g_object_set_data (G_OBJECT (parent), PAPI_CHILDREN, data);
         }
         return 0;
     }