(packaging) Make dmidecode arch specific on debian

The dmidecode package on debian is only available on ia64, amd64 and i386, and
not for other arches such as arm. This pull request makes dmidecode only
required for those arches where it is available. This has the side effect of
making facter on debian arch specific.
(packaging) Add amd64 cows to the cows in build_defaults

Now that dmidecode is an arch specific dependency of facter, it is no longer
possible to build a noarch/all package using one cow per dist. This commit adds
an amd64 cow to each of the dists so that both i386 and amd64 packages are
built for facter.
Merge pull request #416 from haus/packaging/1.7.x/make_dmidecode_arch_specific

Packaging/1.7.x/make dmidecode arch specific