Re: NvP: s.add('x') 100M times

[cblake]

Yup. Just what I was seeing, @b3liever. No `main()`-difference to the RSS 
delta, and a very noticable delta in a non-intuitive direction. So, either our 
intuitions are wrong in a way which should be clarified or there's a problem 
which should be fixed. Maybe a github issue?