Predicate MakeConsistency::reverseRead

Consider code like a.b.f = source(). There is flow from source() to [post] a.b (with an appropriate access path), but we also want there to be flow to [post] a (with an appropriate access path). The data flow library is able to infer this step because there is a read step from a to a.b, as long as the post-update node for a exists.