Relatively common in practice are:
* output with transfer full, which is already covered by
  `regress_test_array_struct_out`,
* input with transfer none, covered by a new
  `regress_test_array_struct_in_none`

Other variants are quite esoteric, but it still might be useful to
include them so that bindings can verify that they are handled
gracefully, e.g., by reporting an error instead of crashing.

Issue #90