Unify TextServer built-in module and GDExtension code.

modules/text_server_adv/script_iterator.h

@@ -31,7 +31,22 @@
 #ifndef SCRIPT_ITERATOR_H
 #define SCRIPT_ITERATOR_H
 
-#include "servers/text_server.h"
+#ifdef GDEXTENSION
+
+// Headers for building as GDExtension plug-in.
+#include <godot_cpp/godot.hpp>
+#include <godot_cpp/templates/vector.hpp>
+#include <godot_cpp/variant/string.hpp>
+
+using namespace godot;
+
+#else
+
+// Headers for building as built-in module.
+#include "core/string/ustring.h"
+#include "core/templates/vector.h"
+
+#endif
 
 #include <unicode/uchar.h>
 #include <unicode/uloc.h>