Add to Cart form should accept a language parameter

As far as I know, the Add to Cart form will currently only respect the current language of a user on the site. For example, I don't believe you could right now have a user viewing the site in English who wanted to see the same node in English / French at the same time view the form in the language of the actual node the form is attached to. I'm not sure what would happen if the form is used directly elsewhere... multilingual stuff is a little foggy fo rme.

Damien's recommendations to resolve the problem are as follows:

1. Add a $language parameter to the Add to Cart form callback.
2. Pass it from the display formatter and use it (respecting fallback rules) to fetch attribute field data from referenced products instead of depending on the metadata wrapper. (I believe that's the idea.)
3. Fallback rules in the event a $language isn't passed should be handled by field_language().

Also, if anyone has a clearer example where the current behavior is limiting, I'd appreciate it.