Bug#364604: apt debug messages: could separate "has broken dep on" cases

[Dan Jacobson <jidanni@jidanni.org>]

Package: apt
Version: 0.6.43
Severity: wishlist

I have an idea for better apt debug messages.
Let's examine two messages seen upon dselect-upgrade.
1. Package rxvt-unicode-ml has broken dep on rxvt-unicode
2. Package libgdal1-dev has broken dep on libgdal1c2a
In 1, the problem was a conflict.
In 2, the problem was the user had marked libgdal1c2a for purge with
dpkg --set-selections.
Thus we see "has broken dep on" includes several different situations
that apt could mention, instead of just saying "has broken dep on" for
all cases.