Stop using M_ASN1_TIME_dup

[reaperhulk]

This macro is going away in OpenSSL 1.1.0.

All it really does is ASN1_STRING_dup((const ASN1_STRING *)a) (where a is an ASN1_TIME).

Filing this so we remember to do something about it. On the cryptography side I will make it so the symbol is still available to avoid breaking older pyopenssl.

[hynek]

Seems like we’re using it in only one place:

pyopenssl/src/OpenSSL/crypto.py

Line 1722 in 1ddb289

copy.revocationDate = _lib.M_ASN1_TIME_dup(original.revocationDate)

[reaperhulk]

I can actually entirely replace the _X509_REVOKED_dup implementation with Cryptography_X509_REVOKED_dup. It is available in cryptography 1.2+ only though, so I can't do it unless the required version is getting bumped for the 16.0 release. Is that the plan? I can't remember now. I'll submit a PR that replaces it + bumps the version but feel free to close it if that's not the plan.

[hynek]

We need 1.3 anyway for the missing bindings.