Re: AIX support

I wrote:
> With the patch attached, I can get through "make installcheck".
> However, I'm unable to attempt "make check-world" because
> src/test/modules/test_cplusplusext doesn't compile:

Ah, I figured out that bit: g++ will take this if you specify -maix64
to it too.  The built module would not have worked anyway without
that, since it'd be 32-bit (AFAICT neither gcc nor g++ react to
the OBJECT_MODE environment variable).

It's not exactly clear why gcc will accept __int128 in 32-bit mode
while g++ won't, but that seems like another good reason to decide
that we won't support 32-bit builds on AIX anymore.

            regards, tom lane