Add: [NewGRF] All callbacks returning D0xx strings, have now the option to return any string id via register 0x100.

src/build_vehicle_gui.cpp

@@ -801,6 +801,9 @@ static std::optional<std::string> GetNewGRFAdditionalText(EngineID engine)
 	if (callback == CALLBACK_FAILED || callback == 0x400) return std::nullopt;
 	const GRFFile *grffile = Engine::Get(engine)->GetGRF();
 	assert(grffile != nullptr);
+	if (callback == 0x40F) {
+		return GetGRFStringWithTextStack(grffile, static_cast<GRFStringID>(regs100[0]), std::span{regs100}.subspan(1));
+	}
 	if (callback > 0x400) {
 		ErrorUnknownCallbackResult(grffile->grfid, CBID_VEHICLE_ADDITIONAL_TEXT, callback);
 		return std::nullopt;