bug#20398: 25.0.50; Clicking `window-divider-last-pixel' in help for `window-divider'

[Glenn Morris]

Eli Zaretskii wrote:

>> M-x customize-face RET window-divider RET
>> 
>> and mouse-clicking 'window-divider-first-pixel' in the doc-string.
>
> That doesn't cause an error, just a message that it's not a variable.

widget-documentation-link-action is surprisingly simplistic.
It doesn't even know that faces exist.
It should do what `help-make-xrefs' does, and use the presence of "face"
etc in the doc string as a cue. Ideally it would reuse the same code.