Fix compilation with external libyaml

third_party/lua-yaml/lyaml.cc

@@ -44,8 +44,9 @@ extern "C" {
 #include <lj_state.h>
 
 #include "yaml.h"
-#include "yaml_private.h"
 #include "b64.h"
+/* Use private header from bundled libyaml for IS_PRINTABLE() macro */
+#include "third_party/libyaml/yaml_private.h"
 } /* extern "C" */
 #include "lua/utils.h"