Just when I was starting to feel comfortable using Hg, this happens. It
appears that between my inexperience with Hg and the non-intuitive
TortoiseHg rebase merge tool, many of the changes I made to
posixmodule.c were lost and as amaury.forgeotdarc remarked, other
commits were reverted.

This means that except for the patches in this ticket, I've lost the
revision history for this work. No biggie.

I've rebuilt the patch from scratch (still against the old code base).
I'm including it here for posterity as draft 8. I'll be attempting once
again to rebase it against the parent's tip. Stay tuned.