Minor documentation tweak

Update the return type for SSL_state in the documentation.
Reviewed-by: NTim Hudson <tjh@openssl.org>
Reviewed-by: NRichard Levitte <levitte@openssl.org>

doc/ssl/ssl.pod

@@ -624,7 +624,9 @@ success or 0 on failure.
 
 =item int B<SSL_shutdown>(SSL *ssl);
 
-=item int B<SSL_state>(const SSL *ssl);
+=item enum HANDSHAKE_STATE B<SSL_state>(const SSL *ssl);
+
+Returns the current handshake state.
 
 =item char *B<SSL_state_string>(const SSL *ssl);