Fix limit train lookahead to signal aspect when starting

From depot and within signal sighting distance (e.g. reverse)

src/pbs.cpp

@@ -996,8 +996,13 @@ void SetTrainReservationLookaheadEnd(Train *v)
 		return;
 	}
 
+	if (v->lookahead->lookahead_end_position > v->lookahead->reservation_end_position) return;
+
 	int32 threshold = v->lookahead->current_position + 24;
 	uint8 known_signals_ahead = 1;
+	if (v->IsInDepot()) {
+		known_signals_ahead = _extra_aspects + 1;
+	}
 	for (const TrainReservationLookAheadItem &item : v->lookahead->items) {
 		if (item.end >= v->lookahead->reservation_end_position) break;
 		if (item.type == TRLIT_SIGNAL) {

src/train_cmd.cpp

@@ -4007,7 +4007,10 @@ static bool IsReservationLookAheadLongEnough(const Train *v, const ChooseTrainTr
 		if (v->lookahead->reservation_end_position >= v->lookahead->current_position + v->reverse_distance - 1) return true;
 	}
 
-	if (v->lookahead->lookahead_end_position <= v->lookahead->reservation_end_position && _settings_game.vehicle.realistic_braking_aspect_limited == TRBALM_ON) return true;
+	if (v->lookahead->lookahead_end_position <= v->lookahead->reservation_end_position && _settings_game.vehicle.realistic_braking_aspect_limited == TRBALM_ON &&
+			v->lookahead->reservation_end_position > v->lookahead->current_position + 24) {
+		return true;
+	}
 
 	TrainDecelerationStats stats(v, v->lookahead->cached_zpos);