Section 9.2.1 includes "attributes-natural-language" in the list of Job
attributes that MUST NOT be settable. However, it seems useful and not hard
to implement, if a user's client sets the wrong natural language, that the
user could change it after job submission, so that messages would come in
the proper (supported) language).
ISSUE 12 - Ok to remove "attributes-natural-language from the list of Job
attributes that MUST be READ-ONLY?