use stable-proposed-updates during pre-release

[Vagrant Cascadian <vagrant@freegeek.org>]

i hate to propose new ideas at this point in the release cycle, but i realized
that since we haven't yet "released" we might want to consider pulling in
lenny-proposed-updates by default in preparation for a release. this has some
advantages and disadvantages:

pros:

* we don't end up releasing Debian-Edu only to find out the next point release
  of Debian breaks something.
* we give a some testing back to Debian regarding proposed changes.

cons:

* we might end up with a few packages on the CD/DVD that never make it into a
  point release.
* we might end up with more inconsistancies between network and CD/DVD
  installs.
* we'd have to remember to revert it as soon as we release.


i think the technical changes we would have to make would simply be setting in
the debian-cd build configuration:

  export PROPOSED_UPDATES=lenny-proposed-updates

or maybe:

  export PROPOSED_UPDATES=stable-proposed-updates


thoughts?

live well,
  vagrant