Add option --ignore-erroneous-benchmarks to table-generator.py
that can be used to ignore results where an error occurred during
benchmarking, as flagged by the previous commit in the result file.

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@13431 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c