Add OpenSSL bindings for TLS Finished message.

Add OpenSSL bindings for TLS Finished message, socket type.
Add OpenSSL binding to check if TLS session is reused.

The TLS Finished message can be used in an application to calculate Channel Bindings for TLS (RFC 5929, RFC 5056). Channel Bindings for TLS can be used to detect MiTM attacks with valid certificates.