This one adds a separate new case that has to be parsed differently - if
a hello-retry-request is sent, only the namedgroup is sent - without the
additional key material.
Support for the legacy extension is retained.
The way in which TLS 1.3 is negotiated was changed slightly in later
revisions of the standard. The final version is only sent in an
extension - while the version field in the server hello still shows TLS
1.2.
This patch makes ssl.log show the correct version again.