Add cdd_remove_negative

[magoorden]

When a CDD is used in the context of timed-automata, clock values cannot be negative. Converting a CDD that allows negative clock values to a DBM results in an invalid DBM. The method cdd_remove_negative removes all negative clock values from a CDD.

[mikucionisaau]

You have added a new function. Could you please add a unit test for it?
It should model your described case, fail without your patch and pass with your patch.

[mikucionisaau]

Could you please do a rebase on your branch so that the tests would work on Windows?
like:

git checkout main
git pull
git checkout add-cdd_remove_negative
git rebase main
git push --force

Please be carefull: stop if any of the intermediate commands fail

[magoorden]

Done, and I see that now all checks pass, including the Windows one 😄.