Update version docs

Make it clear that you should not attempt to get the version before the
first handshake is complete.

Fixes #2893
Reviewed-by: NRichard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6013)

doc/man3/SSL_get_version.pod

@@ -20,15 +20,14 @@ protocol information of a connection
 =head1 DESCRIPTION
 
 SSL_client_version() returns the protocol version used by the client when
-initiating the connection.
-
-SSL_get_version() returns the name of the protocol used for the
-connection.
+initiating the connection. SSL_get_version() returns the name of the protocol
+used for the connection. SSL_version() returns the protocol version used for the
+connection. They should only be called after the initial handshake has been
+completed. Prior to that the results returned from these functions may be
+unreliable.
 
 SSL_is_dtls() returns one if the connection is using DTLS, zero if not.
 
-SSL_version() returns the protocol version used for the connection.
-
 =head1 RETURN VALUES
 
 SSL_get_version() returns one of the following strings:
@@ -57,7 +56,7 @@ The connection uses the TLSv1.3 protocol.
 
 =item unknown
 
-This indicates that no version has been set (no connection established).
+This indicates an unknown protocol version.
 
 =back