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_schema.h b/src/tree_schema.h
index cb2489e..f9c3205 100644
--- a/src/tree_schema.h
+++ b/src/tree_schema.h
@@ -24,14 +24,17 @@
 
 #include "log.h"
 #include "tree.h"
-#include "tree_data.h"
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 struct ly_ctx;
+struct ly_path;
 struct ly_set;
+struct lys_module;
+struct lysc_node;
+struct lyxp_expr;
 
 /**
  * @page howtoSchema YANG Modules