Update 3rd-party libraries

[eXpl0it3r]

Currently the SFNUL is a not the best choice to pick, as the dependencies haven't been updated in a long time. Maybe it would be possible to get ASIO and http-parser to a more recent version, but the customization done to Botan seems hard to understand and reapply for newer versions.

Since Botan provides the secure TLS layer, it's critical that it's updated to the latest version to ensure that newly surfaced security issues have been fixed.

Would be great if you could put in some effort to get it update. Maybe Botan cloud also be evaluated for SFML?