Revert "Fixed #1494 -- switch which define we look for for SSLv3 disable...

This reverts commit facea9a7861ac1ecc7948474766cae0f842b3469.

Fixes #1550 

This is causing significant issues for users of distributions where `OPENSSL_NO_SSL3` is currently defined. We should probably backport this fix to a 0.7.1 as well.