Mac-Carbon Makefile.PL 64-bit Check

I should add a check for 64-bit mode to the Mac-Carbon Makefile.PL. This will save a lot of hassle if I can give a nice error message, with a link to more information, up front.

I can't test this easily, though, since I don't yet have a 10.6 64-bit box (it's only on an original MacBook Pro, which is 32 bits). I will upgrade to Snow Leopard soon. I could try to make my own perl before then, but I don't know it would work the same way. So. If you want to help, now's your chance!

First thought is Config, but we all know Config can be flaky. For example, on my 32-bit box:

$ perl -V:use64bitall

use64bitall='define';

Doesn't really help. I don't know if $Config{intsize} would be 8 on a 64-bit perl. It's 4 on this 10.6 32-bit perl. I do know you should be able to call perl with VERSIONER_PERL_PREFER_32_BIT=yes to give you 32-bit perl, instead of the default 64-bit perl.

So anyway ... if you can figure out a way to know, under 10.6 stock perl, if I am running under 32-bit perl or 64-bit perl, let me know.