xubuntu patch

[Luzius Thoeny]

Freddy Martinez wrote:
> please review the common tasks patch, particularly the part mentioning
> repositories. I am not certain what the information on the link tells the
> user.
>
> <xref linkend="extra-repositories"/>
>
> I also added a bit of information as well. Let me know what you think.

applied. as of this commit, xubuntu docs are officialy in string freeze 
too :)

luzi