Asynchronous nntp.el

[Lars Magne Ingebrigtsen <larsi@ifi.uio.no>]

I have rewritten nntp.el to be totally asynchronous.  Process filters,
callback functions -- a very flexible architecture.  I'm moving the
`nntp-asynchronous-' stuff (that was used for article prefetching) up
into the Gnus code proper, so that all other future backends capable
of being asynchronous don't have to duplicate that code.  (For
instance -- there's no reason why nnml using ftp to read messages
shouldn't be asynchronous.)

When I get the whole thing working properly, writing functions for
postponed commands (and stuff) shouldn't be much work.

-- 
(domestic pets only, the antidote for overdose, milk.)
  larsi@ifi.uio.no * Lars Ingebrigtsen