Bug#27917: apt: doesn't handle virtual packages nicely

[<gorgo@nokia.hu>]

Package: apt
Version: 0.1.6

# apt-get install netpbm
Updating package status cache...done
Checking system integrity...ok
The following extra packages will be installed:
  netpbm1 bc
The following NEW packages will be installed:
  netpbm1 netpbm bc
0 packages upgraded, 3 newly installed, 0 to remove and 115 not upgraded.
Sorry, but the following packages are broken - this means they have unmet
dependencies:
  netpbm: Depends:c-shell

c-shell is provided by tcsh and csh. I understand that apt should not choose
one of them and install it, but at least it should tell about them to the
user so he can after that do an 
apt-get install netpbm [t]csh

-- System Information
Debian Release: 2.0
Kernel Version: Linux chameleon 2.0.35 #1 Thu Aug 13 12:41:56 CEST 1998 i586 unknown

Versions of the packages apt depends on:
ii  libc6           2.0.7t-1       The GNU C library version 2 (run-time files)
ii  libstdc++2.8    2.90.29-0.6    The GNU stdc++ library (egcs version)