Allow different protocol version when trying to reuse a session

We now send the highest supported version by the client, even if the session
uses an older version.

This fixes 2 problems:
- When you try to reuse a session but the other side doesn't reuse it and
  uses a different protocol version the connection will fail.
- When you're trying to reuse a session with an old version you might be
  stuck trying to reuse the old version while both sides support a newer
  version

Signed-off-by: Kurt Roeckx <kurt@roeckx.be>
Reviewed-by: Viktor Dukhovni <viktor@openssl.org>

GH: #852, MR: #2452

ssl/ssl_err.c

@@ -634,6 +634,8 @@ static ERR_STRING_DATA SSL_str_reasons[] = {
      "ssl session id context too long"},
     {ERR_REASON(SSL_R_SSL_SESSION_ID_HAS_BAD_LENGTH),
      "ssl session id has bad length"},
+    {ERR_REASON(SSL_R_SSL_SESSION_VERSION_MISMATCH),
+     "ssl session version mismatch"},
     {ERR_REASON(SSL_R_TLS_CLIENT_CERT_REQ_WITH_ANON_CIPHER),
      "tls client cert req with anon cipher"},
     {ERR_REASON(SSL_R_TLS_HEARTBEAT_PEER_DOESNT_ACCEPT),