[NNTP] Snapshot 5

[Clive D.W. Feather]

I've finally found the round tuit and done a new snapshot, available at the
usual places:

<http://www.davros.org/nntp-texts/draft25.pre-5.txt>
<http://www.davros.org/nntp-texts/draft25.pre-5.html>

The major changes are:
* The capability and generic extension stuff has been significantly
  rewritten and reorganised. Most of it is now in a new section 3.6.
  The CAPABILITIES command (5.2) is therefore much simpler.
* The standard extensions section 8 now only addresses the three
  extensions itself, not the generic material (which is now 3.6.4-5).
* The LIST command (7.6) has been rewritten as requested by many.
* Consequential changes to the formal syntax.
* Section 9 (deprecated commands) is now a placeholder; depending on the
  final MODE READER decision, it might disappear.

I have *not* done anything about re-presenting the transit/reader split,
or the three standard extensions, as packages of capabilities. I think it's
a good idea, but I thought it was best to do a snapshot first.

Before I go further, however, I need to bring up one point related to this.
Consider a server that doesn't implement IHAVE and doesn't implement HDR.
Under the current specification, it MUST return 502 to the former command
but 500 to the latter, because IHAVE is a core command while HDR is an
extension command. If we're going to simply make them different
capabilities, then should we be rationalising this (preferably by using 500
in both cases)? Or do we just live with it as an anomaly?

-- 
Clive D.W. Feather  | Work:  <clive at demon.net>   | Tel:    +44 20 8495 6138
Internet Expert     | Home:  <clive at davros.org>  | Fax:    +44 870 051 9937
Demon Internet      | WWW: http://www.davros.org | Mobile: +44 7973 377646
Thus plc            |                            |