Decide on how to deal with mh_recover on Octave

Various unit test fail on Octave, because the mh_recover option does not work properly under Octave as there are differences in setting the random number generator. We can either

• disable the check in the unit test and accept that the behavior of mh_recover is different under Octave and Matlab (and then document this)
• or provide an error under Octave when someone tries to use this option