proposed ISO 639 change for "arn"

[Caoimhin O Donnaile]

I see, for what it is worth (and I am no expert so I don’t know), that the 
Linguistlist Multitree Composite Tree, “South American Isolates”:

   http://multitree.org/trees/South%20American%20Isolates:%20Composite@695937

has Hulliche included within Mapudungu (code arn) as one of 11 named 
“dialects”.

Caoimhín