make bench fails without Alt-Ergo 2.3.3
the API part of the bench fails if specific version 2.3.3 of Alt-Ergo is not installed.
The test should be relaxed so as to succeed with any recent version of Alt-Ergo.
Since the result of the test depends on the number of steps taken by Alt-Ergo, the output should be filtered somehow to avoid failure when only the number of steps is different