libyang CHANGE review header includes

The plugins_types.h was supposed only for implementing data type plugins
code, so I've removed it from libyang.h (now it is supposed to be
included explicitly).
diff --git a/src/tree_data_free.c b/src/tree_data_free.c
index 53d80ca..192f63e 100644
--- a/src/tree_data_free.c
+++ b/src/tree_data_free.c
@@ -17,8 +17,10 @@
 
 #include "common.h"
 #include "hash_table.h"
+#include "log.h"
 #include "plugins_types.h"
 #include "tree.h"
+#include "tree_data.h"
 #include "tree_data_internal.h"
 #include "tree_schema.h"