Re: Annoying build warnings from latest Apple toolchain

I wrote:
> Assuming that this problem is restricted to initdb, which I think
> is true, probably the best fix is to cause the initdb link *only*
> to link libpgcommon before libpq. Every other non-backend program
> is interested in libpq's encoding IDs if it cares at all.

The more I thought about that the less I liked it. We're trying to
get away from link order dependencies, not add more. And the fact
that we've had a latent bug for awhile from random-ish changes in
link order should reinforce our desire to get out of that business.

So I experimented with fixing things so that the versions of these
functions exported by libpq have physically different names from those
that you'd get from linking to libpgcommon.a or libpgcommon_srv.a.
Then, there's certainty about which one a given usage will link to,
based on what the #define environment is when the call is compiled.

This leads to a pleasingly small patch, at least in the Makefile
universe (I've not attempted to sync the meson or MSVC infrastructure
with this yet). As a bonus, it should silence those new warnings
on AIX. A disadvantage is that this causes an ABI break for
backend extensions, so we couldn't consider back-patching it.
But I think that's fine given that the problem is only latent
in released branches.

Thoughts?

regards, tom lane