Reason for patch.
Low flying planes should crash against mountains.

Patch List
21964 : Add: Button in airport construction screen.
with function "CmdBuildAirWayPoint" to place air waypoint.
The function is still the same as bouy placing function. "CmdBuildBuoy"
21965 : Add: Enable builting Waypoint air on land.
STATION_BUOY with transmitter.
21966 : Add: Prepare identical to and from flight path
for aircrafts.
21967 : Add: Inserting orders.
Fix: Change Order::GetLocation procedure, 'airport' is false for wapoints.
To do: Solve distance too far problem.
21968 : Add: Make air crafts fly to waypoints.
21969 : Add: Calculate the distance between landing places.
Air waypoints get a little distance bonus.
Don't leave planes stuck on platform when distance too far but send them to hangar.
Conditional orders only to airports.
flag VAF_DEST_TOO_FAR is only removed when situation resolved.(futue use.)
21970 : Fix: Air waypoint button was not added to the Script API.(adf88)
21971 : Fix: WaypointWindow was crashing and displaying wrong vehicle icon. Can't rely on 'BaseStation::facilities' while waypoint is destroyed.(adf88)
21972 : Fix: When building air waypoints, include also the cost of foundation.(adf88)
21973 : Fix-ish: Return more descriptive "Can't build on water" error when trying to place air waypoints on water.(adf88)
21974 : Add: More descriptive error message when trying to create conditional order to waypoint air.
21975 : Add: Don't allow adding conditional orders with destiny too far.
21976 : Change: When checking order distance do it between stations when cloning airplanes.
21977 : Fix: Aircraft distance handles conditinal orders more correctly in loop.
Fix: Typo in IsDestinationTooFar func.
ToDo:
1: Solve circling waypoint when only one left. (now aircaft is stuck because of direction.)
One way to solve this is changing order of entry points but the flight pattern becomes ugly.