Rewrite the ATC logic

Now signals store speed information with a timeout for this data's validity

src/vehicle.cpp

@@ -2417,6 +2417,7 @@ void VehicleEnterDepot(Vehicle *v)
 			ClrBit(t->flags, VRF_TOGGLE_REVERSE);
 			t->ConsistChanged(CCF_ARRANGE);
 			t->reverse_distance = 0;
+			t->signal_speed_restriction = 0;
 			t->lookahead.reset();
 			if (!(t->vehstatus & VS_CRASHED)) {
 				t->crash_anim_pos = 0;