Bug#685215: Apt pinning is broken

[Kernc <kerncece@gmail.com>]

Namely, what I, as a user, would like only is that pinning per package
(wildcarded) name or version works, and that those more specific pins are
propagated to EDSP/CUDF dumps, i.e. in the EDSP dump, the APT-Pin field for
"package=chromium,version=whatever-is-available-in-unstable" stanza says
505 (as per above /etc/apt/preferences) instead of 501 as it does now.

If I got it wrong, and the current implementation is indeed correct, I'd
very much care for having the broad ideas behind it explained to me.
(Though I doubt it as maintainers have before admitted to behavior being
kind of fuzzy.)