Use own copy of dpkg architecture table

dak uses dpkg's architecture tables to test for valid combinations. It reads the tables out of the installed version of dak, aka the version from the current stable distribution.

The stable release team rejected updates to dpkg in the last two rounds on unrelated grounds. Also the only reason to update these tables in stable in the first place seems to be dak.

Right now, not accepting packages with new architectures mentioned anywhere make it impossible to get some basic packages ready, like linux or glibc. And due to deficit in the ports-archive, this means that there can be no usable installer.

This merge request just adds our own copy of the tables. They can be updated more swiftly with a simple request.