g_callable_info_free_closure with new APIs
g_callable_info_destroy_closure. The pointer from to
g_callable_info_create_closure is passed to
g_callable_info_get_closure_native_address to obtain another pointer equivalent to the return value from the old
prepare_closure API and then is saved to a new field in PyGICClosure. The value of the new field is used for freeing with
g_callable_info_destroy_closure. The previous code called
g_callable_info_free_closure which does nothing and leaks memory resulting in issue #556.