Add current order (station, waypoint or depot) condition variable.

Adjust item bit allocations:
* Increase cond flags from 2 bits to 3 bits, for future expansion.
* Use 2 bits remaining in adjacent gap for an auxiliary type field.
  This is used for the type (station, waypoint, etc.) of order tests.
Perform a linear scan of the program pool when deleting a station,
waypoint or depot.

src/station.cpp

@@ -26,6 +26,7 @@
 #include "core/random_func.hpp"
 #include "linkgraph/linkgraph.h"
 #include "linkgraph/linkgraphschedule.h"
+#include "tracerestrict.h"
 
 #include "table/strings.h"
 
@@ -137,6 +138,8 @@ Station::~Station()
 	/* Now delete all orders that go to the station */
 	RemoveOrderFromAllVehicles(OT_GOTO_STATION, this->index);
 
+	TraceRestrictRemoveDestinationID(TROCAF_STATION, this->index);
+
 	/* Remove all news items */
 	DeleteStationNews(this->index);