LDAPURL: Null bytes before escaping

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

I suggest that LDAPURL mentions that:

(1) Before URL escaping is applied, the extensions may contain
    null bytes.  No other component may.
(2) The LDAPURL cannot contain null bytes [or 'null characters'].

That can be deduced from various RFCs/drafts (well, I assume there is
some RFC which says this about the hostport component), but it would be
nice to have it all in one place.

-- 
Hallvard