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/waypoint.cpp

@@ -15,6 +15,7 @@
 #include "window_func.h"
 #include "newgrf_station.h"
 #include "waypoint_base.h"
+#include "tracerestrict.h"
 
 #include "safeguards.h"
 
@@ -54,4 +55,5 @@ Waypoint::~Waypoint()
 	if (CleaningPool()) return;
 	DeleteWindowById(WC_WAYPOINT_VIEW, this->index);
 	RemoveOrderFromAllVehicles(OT_GOTO_WAYPOINT, this->index);
+	TraceRestrictRemoveDestinationID(TROCAF_WAYPOINT, this->index);
 }