if a struct has a member that is a function pointer with `external`
attribute, and such a member is called, it is currently incorrectly
treated as a public getter in SMTEncoder.
The proposed fix is to make SMTEncoder::publicGetter more strict in
deciding whether an expression is a public getter.
The added condition, that the access happens on a state variable, is
exactly what is checked later with an assertion that is currently
failing.
Martin Blicha
8ca453f82e