[patch] native AMD64 support

Hi Markus,

Thanks for this interesting patch!

It looks okay to me, but our C/C++ Front End guru is away right now. I
would rather defer to him on this patch. He might not get to it until
next week so I just wanted to let you know that there might be a bit of
a delay before this patch hits mainline. I've already committed your
configure changes.

Reid.