additions to ISO 639 and the IANA language subtag registry

[Frank Ellermann]

Peter Constable wrote:

> I'm just trying to understand what the operation principles
> are here.

The principle is "stability forever", you can never add a new
subtag x if an old subtag x is already registered, deprecated
or not.  

Conflicts across different types of subtags are okay, the 3066,
3066bis, and matching syntax guarantee that region XY cannot
be confused with language XY.  Dito "extlang" when/if it will
be enabled in 3066ter,  Dito Debbie's alpha4 codes when/if
that will be added.

Everything from the source standards has to be registered if
there is no conflict for the given type.  With detailed rules
for 3166-cases like CS, because that's likely.  For languages
3066bis quotes the promise that there never will be conflicts.
IIRC scripts have the same property.

                           Bye, Frank