Needed to relax the precision for the verification results a little bit, there turns out to be more variation between machines and versions than expected as the convergence criteria are set rather loose to finish in a short enough time.

Deleted examples on a CentOS 8 cluster for configurations that are no longer supported by the benchmark.

Update to the build instructions, with a further example, and a patch to avoid crashes during the tests with certain compilers (essentially a backport of 19.8.1 code to 1.5.2)