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.