bug#30707: describe-variable misses linking linkable changed items

[積丹尼 Dan Jacobson]

I do
(describe-variable (quote browse-url-browser-function))
and see in *Help*:

   browse-url-browser-function is a variable defined in ‘browse-url.el’.
   Its value is ‘browse-url-chromium’
   Original value was
   browse-url-default-browser

The problem is browse-url-default-browser should be a blue link, but was
not detected as linkable.

So the user has to do
(describe-function (quote browse-url-default-browser))
to learn about it, instead of just being able to click it!

See, it really exists:
browse-url-default-browser is a compiled Lisp function in
‘browse-url.el’.