Deserialize ASIdentifiers in libcrypto

Deserialize ASIdentifiers in libcrypto

Let the RFC 3779 code in libcrypto do its job: deserialize the ASIdentifiers
extension using X509V3_EXT_d2i() and then simply walk the returned struct.
This replaces quite a bit of low level ASN.1 fiddling with much simpler
reaching into structs with names that have some meaning.

Additionally, RFC 6487, 4.8.10 forbids RDI entries, so throw an error
instead of ignoring them.

ok claudio