[check] error message "translation"

Hi all,

I was looking at how "localizable" we had made the validator with the
templating code, and noticed that one of the obstacles would be the
translation of the error messages. 

The explanations could easily be translated, thanks to the
error_messages file, but the error messages are a different business. I
suppose that with a bit of regexp magic, we could replace (in sub
report_errors())  $err->{msg} with what the configuration file says it
is. This is not trivial since the messages are not static sentences,
they're "element FOO is bad", and we'd need to extract FOO.

On the other hand, having this mechanism in place would also allow for
clearer error messages (without systematically having to rely upon the
explanations to make the errors understandable).

Thoughts?
-- 
olivier