Re: waitpid in pg_basebackup

I wrote:
> I agree, let's drop the support for waitpid() not being present.

BTW, some digging in the commit logs shows that postmaster.c's
existing support for using wait3 in place of waitpid was added in
commit a5494a2d92a2752c610b8b668a7d33478e90c160, "Various patches for
nextstep by GregorHoffleit".  NextStep is presumably quite dead by
now, and anyway we officially pulled support for it as of 9.2.

I will go ahead and remove that code.
        regards, tom lane