os.arch "amd64" or "x86_64"?

[Henri Gomez]

> The JDK 6 "java" command on OS X mentions this value as well, so it technically isn't even restricted to internal developer details (though most non-developers on OS X would never run "java" from the command line).
>
>>java -?
> …
> where options include:
>    -d32          use a 32-bit data model if available
>    -d64          use a 64-bit data model if available (implies -server, only for x86_64)
> …

Apple JVM 1.6 report i386 with -d32 and x86_64 with -d64.
I guess we should do the same in Universal modes for OpenJDK 7 and higher