Comment nitpicking in predicate_refuted_by_recurse()

Attached find patch that makes certain comments in
predicate_refuted_by_recurse() clearer, for example:

-        * AND-clause R=> AND-clause if A refutes any of B's items
+        * AND-clause A R=> AND-clause B if A refutes any of B's items

The comment above the function is written using the latter style so adopt
the same style inside the function.

Thanks,
Amit