Only run in pathfinder case if deny or penalty are present.
Only run in is safe waiting tile case is reserve through is present.
Presence is determined at program validation time and cached in the
program structure.
Validator now checks for unknown non-conditional instructions.
This only changes the behaviour of PBS reservations which
would otherwise terminate at a PBS signal.
If the signal restriction sets the reserve through state,
the reservation continues through the signal, and the signal
is set to green.
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.
This is a port of the tracerestrict/routing restrictions feature
from TTDPatch.
At present this implements if tests (train length only),
and pathfinder deny and penalty actions.
This requires the use of YAPF. Note that restrictions are only evaluated
within the YAPF lookahead distance.
Jonathan G Rennison