There are only two measurement systems that locales use: US and metric.
For the former, move to copying the en_US locale, while for the latter,
move to copying the i18n locale. This lets us clean up all the stray
comments like FIXME.
There should be no functional differences here.
lang_lib (which reflects ISO 639-2/B (bibliographic) codes) and
lang_term (which reflects ISO 639-2/T (terminology) codes) should be
identical except for those languages for which ISO 639-2 specifies
separate bibliographic/terminology values.
I used this Library of Congress page as the source:
http://www.loc.gov/standards/iso639-2/php/code_list.php