Follow-up r112479

Follow-up r112479
* Add @since, fix indentation.
* Change default from 'all' to 'mw' as it's the most used (so default fetchLanguageNames() is equivalent to default getLanguageNames()).
* Add the include parameter also to fetchLanguageName() as it's needed in Parser: interlanguage links should only take into account mediawiki names. (Doesn't make a difference with how the functions are now, but could have been later.)