Translation of newsletter footer

Sent newsletters always have a footer saying "Click here to unsubscribe from this newsletter" and I just noticed that it is not properly translated when the newsletter is sent from a cronjob. The reason is that although t() is called on that string, the current language is always English during cronjobs.

A proper behavior would have the footer match the newsletter's language. I'm providing a patch that does this, but I'm warning you: it is very ugly! I'm not sure it should ever be committed, but it may be useful to some people until a better solution is found.

Making the footer text part of the node could be a better solution. This way no hack would be needed, and the footer would be in whatever language the node's author used. Simplenews could provide a default text (translated with t()) when creating the node. Any opinions on this?