Traceability for record field names in counterexamples.
In wp, eval_match is used to replace record fields with simple variables of the same type. Originally, all labels from the variable that field was accessed were copied to new variables representing fields of this variable. Therefore also "model_trace:var_name" label was copied and thus the field had name "var_name" in the counterexample. This commit solves this problem by appending names of the fields to "model_trace:*" label of new variables representing record fields.