When I try to install libtcl package using "apt-get install libtcl" i get this:

The following packages have unmet dependencies:
libtcl: PreDepends: /sbin/postun_ldconfig but it is not installable
E: Unmet dependencies. Try 'apt-get --fix-broken install' with no packages (or specify a solution).

And 'apt-get --fix-broken install' doesnt solve anything.
What exactly is postun_ldconfig? I cant find it on any rpm or source site.