UN M.49 in language tags & locales

[Don Osborn]

Trying to catch up on what the current rules are on use of 3-digit 
region codes in language tags and got lost in the wording of RFC 5646. 
Also interested to know if these UN M.49 codes can still be used in locales.

This is for general info for the benefit of African localizers, not for 
a specific localization project. Is there any quick guide that covers 
this particular issue?

BTW, it looks like the Territory Containment table at 
http://www.unicode.org/cldr/charts/latest/supplemental/territory_containment_un_m_49.html 
needs to be updated to show South Sudan in Eastern Africa (per 
http://unstats.un.org/unsd/methods/m49/m49regin.htm ). I'll file a bug 
report on that.

Don Osborn