Print intermediate evaluation results for some ASSERTed expressions

* The reports of errors signaled by ASSERT now print intermediate
  evaluation results under the following conditions:
   1. The ASSERTed expression is known to be a function call.
   2. Arguments in the call are not constants.

* Test the new feature in condition.impure.lisp.

* Original patch from Alexandra Barchunova; closes lp#789497.