Re: setuid(geteuid());?

I said:
> On machines that have setreuid(), or even better setresuid(), we could
> force the ruid (and suid for good measure) to match euid.  Otherwise we
> probably should refuse to start unless getuid matches geteuid.

But on third thought, it's not worth the trouble of adding two more
configure tests to support a configuration that I doubt anyone uses
anyway (ie, setuid postgres executable).  Let's just remove the setuid()
and add a check for getuid() == geteuid() in main.c.

Peter, unless you've already started in on this, I can take care of it
--- I see a couple of other nits I want to fix in those two files, too.
        regards, tom lane