🚀 go-pugleaf

This is an advance plug for an nntp.el that I'm rewriting from
scratch.  It has minor speedups all over, but the major speedup is it
understands Geoff Collyer's news overview database and will use the
XOVER command if it can.

The prototype I'm using can read and parse about 500 headers in about
2.5 seconds.  This is on a Sun4/20 talking to a Sun4/380 NNTP server,
under optimal conditions.  (Suboptimal conditions might make it about
twice as slow.)

2.5 seconds is still slower than I'd like, but I don't think I can
improve it much in pure elisp.  And there are plenty of other things
in GNUS that are currently much much slower (like threading).

I'm halfway through a production rewrite.  It should be ready in a few
days, barring accidents.  The production version may be be slightly
slower, but not significantly so.

Remember, this major speedup only applies if you have news overview
and the XOVER command, so start upgrading your news system now!

(Some restrictions may apply.  Void where prohibited by law.)
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