build,src: remove sslv2 support

SSLv2 has been deprecated and known broken for nearly twenty years now.

I made SSLv2 support opt-in well over a year ago in commit 39aa8940 and
now this commit removes it entirely.

PR-URL: https://github.com/iojs/io.js/pull/290


Reviewed-By: Fedor Indutny <fedor@indutny.com>
Reviewed-By: Rod Vagg <rod@vagg.org>