Revert "GObject: prevent installing properties after init"

This reverts commit ddb0ce1421.

Conflicts:
	gobject/gobject.c

https://bugzilla.gnome.org/show_bug.cgi?id=698614

gobject/gtype.c

@@ -4818,13 +4818,3 @@ g_type_ensure (GType type)
   if (G_UNLIKELY (type == (GType)-1))
     g_error ("can't happen");
 }
-
-gboolean
-g_type_is_in_init (GType type)
-{
-  TypeNode *node;
-
-  node = lookup_type_node_I (type);
-
-  return node->data->class.init_state != INITIALIZED;
-}