Bring back ASN1_seq_pack(), ASN1_seq_unpack(), ASN1_pack_string() and

Bring back ASN1_seq_pack(), ASN1_seq_unpack(), ASN1_pack_string() and
ASN1_unpack_string() from the NO_ASN1_OLD purge; turns out that some Ruby
extensions still use them, unfortunately, so we need to give them some more
time to catch up on ``recent'' interfaces.

Riding on the libcrypto major bump.