don't prematurely shut down socket -- use SSL_shutdown

demos/ssl/cli.cpp

@@ -97,7 +97,7 @@ void main ()
 
   err = SSL_write (ssl, "Hello World!", strlen("Hello World!"));  CHK_SSL(err);
   
-  shutdown (sd, 1);  /* Half close, send EOF to server. */
+  SSL_shutdown (ssl);  /* send SSL/TLS close_notify */
   
   err = SSL_read (ssl, buf, sizeof(buf) - 1);                     CHK_SSL(err);
   buf[err] = '\0';