As stated. Yes, it's already in the AMD64 FAQ, but seeing as the default profile is a multilib profile, we should have an example of <comment>"if you want it...."</comment> in the kernel configuration chapter. As it doesn't seem to be turned on by default. This way we get to make users and the AMD64 team happy.
Er, never mind. Seems it is enabled by default; I just couldn't get a clean testing env. Move along, nothing to see here.