Openssl: No-ssl2

Disables the sslv2 ciphers in OpenSSL. 

This has been under [discussion](https://github.com/Homebrew/homebrew/pull/30504) for quite some time. I have tested this change against Homebrew provided curl, subversion, wget, lynx, openssh, nmap, python & python3 without encountering any issues thus far. I’ve also done limited testing with OpenSSL itself and haven’t found any issues with the core functionality. The code was sufficiently updated between OpenSSL 1.0.1h and 1.0.1i to roll with -no-ssl3 as well, but I think that move is a tad premature. 

Given the recent OpenSSL release, I think if we’re going to press ahead with -no-ssl2 this is the time to implement it. If any issues crop up we can always revert, but I’m fairly confident at this point this option can be safely configured in without consequences for end users.