"mis" update review request

[Frank Ellermann]

Harald Alvestrand wrote:

> ISO 639 has zxx. That doesn't mean that 4646ter needs to use it.
> If I'm using "we" on this list, I mean "the users of 4646ter".

I hope you mean 4646bis... :-)  For RFC 4646 there's no procedure
to deprecate problematic ISO 639-2 subtags.  Adding a warning in
the form of a comment is the only available option.  If ISO 639
later redefines "mis" to mean "any" it's compatible with RFC 4646,
the comment could be updated or removed.

If ISO 639 sticks to "mis" as "not in any other collection" then
the comment should help to avoid "mis"-uses for "any" purposes.

If ISO 639 later deprecates "mis" the registry would reflect this,
the comment should help to avoid "mis"-uses for legacy purposes.

Frank