schema compile CHANGE store default values as in lyd_value structure

Use the data trees's structure to store the default values even in
the compiled schema tree. It is necessary for default value validation
and useful for instanciating default nodes in data trees.
diff --git a/src/printer_json.c b/src/printer_json.c
index 7ca29c4..1ef4309 100644
--- a/src/printer_json.c
+++ b/src/printer_json.c
@@ -27,7 +27,7 @@
 #include "tree_schema.h"
 
 /**
- * @brief
+ * @brief JSON mapping of YANG modules to prefixes in values.
  *
  * Implementation of ly_clb_get_prefix.
  */