make it compatible with Coq 8.7, and test that
Turns out Coq 8.7 is 20% faster. :-) Some of this is lost to parallelism though, it seems.
real 11m7.102s user 25m5.797s sys 0m17.457s
real 9m0.417s user 19m40.020s sys 0m16.213s
I reported the fact that I had to change something to make it work again as https://coq.inria.fr/bugs/show_bug.cgi?id=5749.