protocol: Result codes no longer reserved for API

[Hallvard B Furuseth <h.b.furuseth@usit.uio.no>]

In RFC 2251 section 4.1.10 (Result Message), result codes 81-90 were
reserved for the API.  Since Protocol-20, they have not been.
The change is not noted in section C.1 (Changes made to RFC 2251),
nor can I find any discussion about it.

BTW, C.1 also does not note that strongAuthRequired was renamed to
strongerAuthRequired.

-- 
Hallvard