Add gtk_tree_model_rows_reordered_with_length introspectable method

Add introspection friendly version of gtk_tree_model_rows_reordered
with a "_with_length" suffix. This allows language bindings to
safely pass an array with length argument. Use the "Rename to:"
annotation to expose as "gtk_tree_model_rows_reordered".

https://bugzilla.gnome.org/show_bug.cgi?id=684558

gtk/gtktreemodel.h

@@ -361,6 +361,12 @@ void gtk_tree_model_rows_reordered        (GtkTreeModel *tree_model,
 					   GtkTreePath  *path,
 					   GtkTreeIter  *iter,
 					   gint         *new_order);
+GDK_AVAILABLE_IN_3_10
+void gtk_tree_model_rows_reordered_with_length (GtkTreeModel *tree_model,
+						GtkTreePath  *path,
+						GtkTreeIter  *iter,
+						gint         *new_order,
+						gint          length);
 
 G_END_DECLS