Document SSL_SESSION_set_protocol_version()

Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3670)

doc/man3/SSL_SESSION_get_protocol_version.pod

@@ -2,19 +2,27 @@
 
 =head1 NAME
 
-SSL_SESSION_get_protocol_version - retrieve session protocol version
+SSL_SESSION_get_protocol_version,
+SSL_SESSION_set_protocol_version
+- get and set the session protocol version
 
 =head1 SYNOPSIS
 
  #include <openssl/ssl.h>
 
  int SSL_SESSION_get_protocol_version(const SSL_SESSION *s);
+ int SSL_SESSION_set_protocol_version(SSL_SESSION *s, int version);
 
 =head1 DESCRIPTION
 
 SSL_SESSION_get_protocol_version() returns the protocol version number used
 by session B<s>.
 
+SSL_SESSION_set_protocol_version() sets the protocol version associated with the
+SSL_SESSION object B<s> to the value B<version>. This value should be a version
+constant such as B<TLS1_3_VERSION> etc. For example, this could be used to set
+up a session based PSK (see L<SSL_CTX_set_psk_use_session_callback(3)>).
+
 =head1 RETURN VALUES
 
 SSL_SESSION_get_protocol_version() returns a number indicating the protocol
@@ -24,17 +32,21 @@ B<TLS1_VERSION> or B<TLS1_2_VERSION>.
 Note that the SSL_SESSION_get_protocol_version() function
 does B<not> perform a null check on the provided session B<s> pointer.
 
+SSL_SESSION_set_protocol_version() returns 1 on success or 0 on failure.
+
 =head1 SEE ALSO
 
-L<ssl(7)>
+L<ssl(7)>,
+L<SSL_CTX_set_psk_use_session_callback(3)>
 
 =head1 HISTORY
 
-SSL_SESSION_get_protocol_version() was first added to OpenSSL 1.1.0
+SSL_SESSION_get_protocol_version() was first added to OpenSSL 1.1.0.
+SSL_SESSION_set_protocol_version() was first added to OpenSSL 1.1.1.
 
 =head1 COPYRIGHT
 
-Copyright 2001-2016 The OpenSSL Project Authors. All Rights Reserved.
+Copyright 2001-2017 The OpenSSL Project Authors. All Rights Reserved.
 
 Licensed under the OpenSSL license (the "License").  You may not use
 this file except in compliance with the License.  You can obtain a copy