Codechange: Replace vehicle related FOR_ALL with range-based for loops

src/train_gui.cpp

@@ -33,8 +33,7 @@ void CcBuildWagon(const CommandCost &result, TileIndex tile, uint32 p1, uint32 p
 
 	/* find a locomotive in the depot. */
 	const Vehicle *found = nullptr;
-	const Train *t;
-	FOR_ALL_TRAINS(t) {
+	for (const Train *t : Train::Iterate()) {
 		if (t->IsFrontEngine() && t->tile == tile && t->IsStoppedInDepot()) {
 			if (found != nullptr) return; // must be exactly one.
 			found = t;