Instead use a new struct spki_5_tuple_list ** argument for
returning the list. The pint is to support sequences of the form
(sequence (public-key ...)) that implies a subject, but result in
an empty 5-tuple list.
(spki_parse_sequence): Likewise.
(spki_parse_sequence_no_signatures): Likewise.

Rev: src/spki/certificate.c:1.27
Rev: src/spki/certificate.h:1.27