if the station is too far away. Instead, simply return the closest station.
All the code that searches navaids does it's own range checking anyway.
This will make the navlist query functions a bit more useful for other
types of functionality where you may need to lookup a station without
consideration of range (i.e. presetting your position relative to a navaid.)
Modifications to support querying navaid database by station ID (not just
frequency.) Some corresponding changes to testnavs.cxx to test new
functionality.
