bug#21734: 25.0.50; cursor-in-non-selected-windows set to nil in gnus-article-mode for no apparent reason

[Oleh Krehel]

See commit e4a89ccf738861d7b9c4f611185aa0f204c9c208 from 2006 with:

+  (setq cursor-in-non-selected-windows nil)

And the following Changelog entry:

2006-04-12  Reiner Steib  <Reiner.Steib@gmx.de>

        * gnus-art.el (gnus-article-mode):
        Set cursor-in-non-selected-windows to nil.

and no further explanation. If there are no objections, I'd like to
revert this change, since it's useful to see a hollow cursor in case the
buffer with the article isn't selected, and the hollow cursor is the
default in all modes except this one.

If a particular user wants the current setting, it can be set in
`gnus-article-mode-hook'. It's better than having a non-standard value
in one particular mode for all users.