[Tails-dev] Use version instead of release in apt preference…

Hi,

During 0.21 testing, I wondered why apt/preferences reads debian
releases (testing, devel) and not package versions? I think that it
would be more clear, at lease for packages like kernels that we upgrade
manually. What do you think?

I suggest something like the following:

Package: linux-base
Pin: release o=Debian
Pin: version 3.5
Pin-Priority: 999

Package: linux-headers-486
Pin: release o=Debian
Pin: version 3.10+52
Pin-Priority: 999

[...]

Package: linux-headers-3.10-3-common
Pin: release o=Debian
Pin: version 3.10.11-1
Pin-Priority: 999

Cheers