Present helpful message when booting 64-bit medium on 32-bit machine

[Colin Watson]

"""
From: Stuart Langridge <email address hidden>

Can the iso itself detect when it's booted on an i386 system and say
"Hey, you've got the modern Ubuntu disc; what you needed was the
slightly older ("32-bit") disc, which you can get from www.ubuntu.com"
in some sort of nice way? Obviously it's irritating to have downloaded
(or got from someone) a whole disc that doesn't work, but making it
point you in the right direction to fix the problem would be nice.
"""

gfxboot-theme-ubuntu has the ability to detect 64-bitness, but this isn't wired up properly as yet.

[Kees Cook (kees)]

I haven't looked at the gfxboot code, but if it's helpful, here's what the kernel uses for detecting LM:
http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-precise.git;a=blob;f=arch/x86/kernel/verify_cpu.S;hb=HEAD

[Bryan Quigley (bryanquigley)]

Possible dups or alternate ways to go about doing this:
https://bugs.launchpad.net/ubuntu/+source/ubiquity/+bug/272088
https://bugs.launchpad.net/ubuntu/+source/gfxboot/+bug/272087