Fix quirks in logrel for systemf_mu[_state] by adding different quirks

@lgaeher @mueck @bpeters

Subtraction is too hard for PL people, it is better left to pupils in a Grundschule. Therefore, we should aim to never subtract in our code. This merge request removes some spurious subtractions that were introduced due to a Coq quirk.

We also do the same in systemf_mu_state