[tex-hyphen] language tag for Serbian (Serbo-Croatian?) patterns

[Arthur Reutenauer]

> - sh patterns should work ok for Serbian, Croatian, Bosnian, ... and
> were originally created for Latin script only (in the time when this
> was still considered a single language);

  Wasn't it for Cyrillic originally?  I remembered it was the other way
round with respect to what you say, and that's how I told the story in
my e-mail.  But that's the same idea :-)

> We noticed that "sh" has been deprecated, but an interesting fact
> (Arthur may correct me if I'm wrong - I'm speaking out of my memory)
> is that "sh" has first been deleted from tags and later on introduced
> again.

  Yes, exactly: it was removed from the IANA Language Subtag Registry
when it was deleted from ISO 639-1, then added back again after it was
realised that, according to IETF BCP 47 rules, it should never have been
retired (that was after 2008).

	Arthur