Hi,

Jidanni mailed me that TAB doesn't move point to attachments
existing in the bottom of an html article of Gnus like this:

,---- html part
|......
|       ...link...
|               ......
|                       ...link...
|       ......
`----
[2. application/pdf; foo.pdf]...
[3. application/octet-stream; bar.txt]...

An example is attached.

Each link has `shr-map' that overrides `gnus-article-mode-map'
of which the parent is `widget-keymap'.  TAB on a link invokes
`shr-next-link', not `widget-forward', so performing it on the
last link doesn't move point to the attachment, whereas TAB on
the html part other than links, i.e., `widget-forward', moves
point to the next link.  I think the behavior should be the same
as that of non-html articles.

I'm not quite sure if it is the right way, but tried fixing it
as follows: