Different approach to handling the paired-ILS-on-opposite-runways situation. This...

Different approach to handling the paired-ILS-on-opposite-runways situation. This uses additional information we now store (in FGRunway) to be more explicit about the behaviour (i.e only look at paired navids), and crucially, does not misbehave near either threshold. Instead it always switches about the runway midpoint (so back-course/missed-approaches are broken as before), leading to stable behaviour when touching down.

I am pretty confident this is (was, from FS2004) also the 'solution' taken by MSFS.