Fix CVC4 counterexample regex
Sometimes CVC4 prover models are separated by unknown (RESOURCEOUT)
and not
unknown
, for example in SPARK's test N121-026__nonlinear and many others. This is currently not detected as a separator for models and the trailing model triggers unknown (RESOURCEOUT)
in Smtv2_model_parser
.
This PR simplifies the steplimit regex in a298d6ed, and fixes a couple of loosely related issues.