Re: Replace uses of deprecated Python module distutils.sysconfig

I wrote:
> It's a little bit too soon to decide that INCLUDEPY is reliably equal
> to that, but if it still looks that way tomorrow, I'll be satisfied.

As of now, 92 buildfarm animals have reported results from f032f63e7.
Every single one of them reports that all the different methods you
tested give the same answer.  So it looks to me like we should just
go with get_config_var('INCLUDEPY') and be happy.

I guess next steps are to revert f032f63e7 and then retry e0e567a10
with that change.  Who's going to do the honors?

            regards, tom lane