Let the table-generator script directly compute the number of
regressions.
Previously the BuildBot would compute this number from a summary of the
results which was imprecise (if one file became better and one worse,
it would have not detected the regression).

Also add an option that allows to ignore new timeouts,
if there has been a timeout for this file before in one of the other
runs.

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@13144 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c