Make lists self-sortable.
Implement list sorting for ndp_runway data type.
Revert "Implement list sorting for ndp_runway data type."

This reverts commit 1a4a132bb1ee4cde5f3ad10442229f0f45a0861b.
Revert "Make lists self-sortable."

This reverts commit 696500b3228d50fbe4e951d569cd2b1e0b67524d.
Make lists sortable, take 2.

I didn't like the previous implementation.
Add macro to make comparing two structures by identifier.
Make previous macro more robust.
Miscellaneous simplification.

Also load navdata (but don't parse it yet).