Re: Patch: update Bonjour support to the newer non-deprecated API

I wrote:
> I've grown a bit tired of reading the "'DNSServiceRegistrationCreate' is
> deprecated" warnings in OS X builds, and I'm also wondering whether any
> of the recently reported problems with Snow Leopard might trace to our
> use of an API that Apple has been deprecating since 2003. Hence,
> attached is a patch that replaces our use of the DNSServiceDiscovery.h
> API with the more modern dns_sd.h API.

BTW, I cannot find any evidence that our old Bonjour code doesn't work
on Snow Leopard: it compiles, with just the same deprecation warning
as before, and the postmaster runs, and you can see the Bonjour
registration appear with something like 'dns-sd -B _postgresql' ---
and disappear again when the postmaster exits. I had guessed that
Jerry LeVan's DNS issues might be somehow related to this code, but
apparently not.

So I'm inclined to change the code now that we've got a replacement
that doesn't cause the deprecation warning, but there doesn't seem to
be any need to back-patch it.

I will also see about adding a separate boolean control GUC, as
discussed.

regards, tom lane