Merge branch 'robbert/simpl_Z' into 'master'

Consistently block `simpl` on all `Z` operations

See merge request !41
10 jobs for master in 25 minutes and 46 seconds (queued for 1 second)
Name Stage Failure
failed
build-coq.8.6.0 Build
make[1]: *** [theories/numbers.vo] Error 1
make[1]: Target 'all' not remade because of errors.
Makefile:6: recipe for target 'all' failed
make: *** [all] Error 2

real 0m6.632s
user 0m8.964s
sys 0m4.132s
ERROR: Job failed: exit code 1
failed
build-coq.8.6.1 Build
make[1]: *** [theories/numbers.vo] Error 1
make[1]: Target 'all' not remade because of errors.
Makefile:6: recipe for target 'all' failed
make: *** [all] Error 2

real 0m5.156s
user 0m7.812s
sys 0m3.620s
ERROR: Job failed: exit code 1