[Xfce-i18n] add catalan credits

[Benedikt Meurer]

Pau Rul·lan Ferragut wrote:
> 	dear Mr Meurer,

Hey Pau,

> I am Pau Rul·lan, the catalan-moron. My team-mate has translated Terminal
> into catalan, I have already made the commit of the .po but I would like
> to have him apear in the credits. Is this process automatic? If not, could
> you please add him?
> 
> Carles Muñoz Gorriz <carlesmu at internautas.org>
> (the catalan language code is "ca")

Done. Note that the special string "translator-credits" in the .po
should be "translated" as the list of translators for this language. The
list will then appear in the about dialog when running in the given locale.

>      cheers!

greets,
Benedikt