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.h b/src/tree_data.h
index 0b181e1..8a1997e 100644
--- a/src/tree_data.h
+++ b/src/tree_data.h
@@ -29,8 +29,10 @@
 struct ly_set;
 struct lyd_node;
 struct lyd_node_opaq;
+struct lyd_node_term;
 struct lys_module;
 struct lysc_node;
+struct lysc_type;
 
 /**
  * @page howtoData Data Instances