Re: `pg_ctl init` crashes when run concurrently; semget(2) suspected

I wrote:
> I didn't try other BSDen; this might be a NetBSD-ism that Apple
> inherited, or maybe it's common among the BSDen.

A bit more research later: OpenBSD behaves like NetBSD, while
FreeBSD behaves like Linux.  So that's pretty inconclusive about
what the aboriginal behavior was.  I also found that OpenIndiana
behaves like Linux.

For Linux and FreeBSD, it doesn't actually matter to us because
we no longer use SysV semaphores on those platforms.  But this
is a live problem on macOS, NetBSD, OpenBSD.

            regards, tom lane