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_helpers.c b/src/tree_data_helpers.c
index 7c03e49..5a0d98f 100644
--- a/src/tree_data_helpers.c
+++ b/src/tree_data_helpers.c
@@ -19,6 +19,7 @@
 
 #include "common.h"
 #include "context.h"
+#include "dict.h"
 #include "hash_table.h"
 #include "log.h"
 #include "lyb.h"