Re: Centralised architecture detection

I wrote:
> Nathan Bossart reminded me of this thread after I'd independently
> rediscovered the same thing [1].  I agree with standardizing on
> just one spelling of these CPU-type macros.  But I wonder why we
> should invent our own instead of standardizing on gcc's spellings
> (that is, __x86_64__ etc).  The amount of code churn required for
> this patch would drop drastically if we did it that way.  And I
> suspect it would be less likely that we'd need to fixup future patch
> submissions than if we have a homegrown standard.

Concretely, I'm imagining that we'd do more or less the attached in
c.h, and then the rest of the work would just be to remove the
not-very-large number of references to the alternative CPU symbols.

Note that I threw in an "#else #error" branch to ensure that we
successfully identify every architecture.  Even if you don't like
this naming scheme, we should do that with the original patch too.

			regards, tom lane