Managing alternative 639-2 codes for languages

[dportoles]

XSLT generates the conversion to dct:LinguisticSystem to EU language vocabulary (https://op.europa.eu/en/web/eu-vocabularies/dataset/-/resource?uri=http://publications.europa.eu/resource/dataset/language)

It's done directly, without any other checking.

That works fine for the most of languages, but there are several languages that has two 639-2 codes (alternative codes for bibliographic or terminology purposes.

Further info: https://www.loc.gov/standards/iso639-2/php/code_list.php

That's the case for 4 official languages and other languages at national leves such as basque.

I propose to change the XLST code for mapping to existent vocabulary URI.
i.e. BAQ would be mapped to http://publications.europa.eu/resource/authority/language/EUS