KLN89: Fix ARINC 424 loader for airports with parallel runways.

KLN89: Fix ARINC 424 loader for airports with parallel runways.

To load approach data into the KLN89, drop an ARINC 424 format file
named "rnav.dat" into the data/Navaids directory.  The loader has
been tested on the 424-18 data revision, so may need tweaking for
the latest data.  Currently about 97% of the listed US non-precision
approaches are loaded, the majority of the failures appear to be due
to 1-digit runway code offsets between the flightgear airport data
and the ARINC data due to magnetic variation changes.