lost nindex files

[utzoo!decvax!duke!trt]

Lost .nindex files are usually due to file space outages.
The cure, broadcast in net.news some time ago,
is to check for I/O errors in n_close() (and u_close()) in index.c.

However, sometimes .nindex files are STILL lost,
for a reason that completely eludes me.
As a desperate patch, in index.c swap the #define-d values of
UPDATE and READ, so the safer "READ" mode is the default one.
(I do not see how this matters, by the way.)

As a better patch, steal the latest blessed version of Duke news
in /usr/spool/uucppublic/news.tar on either duke or decvax.
It should serve until X.Ybsd news takes over.