cc@mdboom in case there was a reason to omit them.

Ah, pypy3 failure seems relevant. decimal_factorial looks too slow on PyPy3 (with only pure-Python version of the decimal module).

@hugovk, anything else?

I think we can enable decimal_factorial test, but this will need a workaround for pure-Python decimal module. The presence of accelerated module we can detect, trying to import the_decimal module.

1. Either we can lowern andc.prec (we can't use MAX_PREC for pure-Python module) inbench_decimal_factorial()
2. or use different settings conditionally, for pure-Python and C modules