Bug#208874: apt: Upgrade tries to install new libc-udeb as well as existing libc6

[Petter Reinholdtsen <pere@hungry.com>]

[Matt Zimmerman]
> You should never need to install udebs on an installed system, and I
> don't think that apt even tries to handle them intelligently.  If it
> did, it should probably treat them like experimental and never
> install them unless explicitly requested.

I know.  But udebs are debs not following policy, dropping
documentation, licence info and all files not required to get d-i
working, so the problem should affect real debs as well.

Ah, and I forgot to include the command I used to trigger the bug.
This is the command line:

  apt-get update && apt-get -u dist-upgrade