Remove the "pseudopackage" handling of Architecture: all packages for Multi-Arch; instead, Arch: all packages only satisfy dependencies for the native arch, except where the Arch: all package is declared Multi-Arch: foreign. (Closes: #613584)
This has the sideeffect that arch:all packages internally show up as coming from the native arch - so packages with the architecture "all" doesn't exist any longer in the pkgcache