libyang MAINTENANCE cleanup header includes

Use iwyu tool and fix which headers are included
diff --git a/src/xpath.c b/src/xpath.c
index e54198a..d05107f 100644
--- a/src/xpath.c
+++ b/src/xpath.c
@@ -40,6 +40,7 @@
 #include "printer_data.h"
 #include "schema_compile_node.h"
 #include "tree.h"
+#include "tree_data.h"
 #include "tree_data_internal.h"
 #include "tree_edit.h"
 #include "tree_schema_internal.h"