Add SSL presets.

No need to use a separate profile as in X.509, everything we need is already
in ssl_config. Just load appropriate values.
diff --git a/programs/ssl/ssl_server.c b/programs/ssl/ssl_server.c
index 6c837e9..f2f969c 100644
--- a/programs/ssl/ssl_server.c
+++ b/programs/ssl/ssl_server.c
@@ -193,7 +193,8 @@
 
     if( ( ret = mbedtls_ssl_config_defaults( &conf,
                     MBEDTLS_SSL_IS_SERVER,
-                    MBEDTLS_SSL_TRANSPORT_STREAM ) ) != 0 )
+                    MBEDTLS_SSL_TRANSPORT_STREAM,
+                    MBEDTLS_SSL_PRESET_DEFAULT ) ) != 0 )
     {
         mbedtls_printf( " failed\n  ! mbedtls_ssl_config_defaults returned %d\n\n", ret );
         goto exit;