[support] Debian wiki for drupal6 -> drupal7 package upgrade

[Daniel Pocock]

Debian 6 (stable) currently has drupal6

Debian 7 (now in freeze/beta) has drupal7

I've created a wiki page about the transition process for those using
the packages on Debian:

   http://wiki.debian.org/Drupal/Upgrade/From6To7

It would be good to have feedback from people using the packages or from
people more familiar with Drupal than myself.