Enable auto-update for Debian squeeze-lts

Quoting https://wiki.debian.org/LTS

Official security support for Debian GNU/Linux 6.0
(code name "Squeeze") has ended on 31 May 2014.
However long term support for the distribution
is going to be extended until February 2016,
i.e. five years after the initial release.

See https://wiki.debian.org/LTS for more details.
add facts showing available updates

Making use of the apt-check command from the 'update-notifier-common'
package (if available) display the number of available updates, number of
security updates as well as the update package names.
Merge pull request #319 from cloudbuy/master

add facts showing available updates
Merge pull request #321 from raoulbhatia/squeeze-lts

Enable auto-update for Debian squeeze-lts