fix, remove or change to warning: false negatives for cyclic detection

[MartijnR]

False negatives:

• using indexed-repeat() to get the value of the same node in a different repeat instance
• using a predicate that includes ".", e.g. count(//text1[normalize-space(.)=“yes”])

[MartijnR]

I think this can be considered impossible to do properly (i.e. with actual errors). You'd have to run the form engine and detect infinite loops, because:

1. self-references could be very complex via multiple nodes (but we could just leave that out)
2. a calculation could refer to itself to e.g. determine its own ancestor repeat position within the form using indexed-repeat(). If we cannot exclude these false negatives, we'd have to perhaps output a "possible self-referencing warning" instead of an error