Revert "Variadic is as simple as not specifying argtypes."

This reverts commit ef6767ca32ebceac7c0e6855d1db056c2c02662a.
This just happens to work for me, but is not portable. Newer libffi (>=3.11)
has proper variadic support. ctypes hasn't caught up yet.
Make ib_status use same settings as other tests.