data tree REFCTOR move prefix callbacks to plugins types

Meaning they are still public but needed only when
implementing plugins. Common API functions do not
require these callbacks.
diff --git a/src/path.h b/src/path.h
index 2e32f91..d57cd31 100644
--- a/src/path.h
+++ b/src/path.h
@@ -19,6 +19,7 @@
 #include <stdint.h>
 
 #include "log.h"
+#include "plugins_types.h"
 #include "tree.h"
 #include "tree_data.h"