X509_set_subject_name and X509_set_issuer_name copy the object
X509_set_subject_name and X509_set_issuer_name copy the object

So we need to register our own copy for gc. This fixes a memory leak
reported by Wulf.

Ayrx/cryptography,Ayrx/cryptography,Ayrx/cryptography,Ayrx/cryptography