Revert "Fixed #1494 -- switch which define we look for for SSLv3 disabled. We're now using the same one as CPython."

This reverts commit facea9a7861ac1ecc7948474766cae0f842b3469.
Merge pull request #1587 from reaperhulk/backport-no-ssl3-fix

backport OPENSSL_NO_SSL3 change to 0.7.x branch