bug#20664: 25.0.50; Customize: Link option or face name to the source definition

[Drew Adams]

> > FWIW: With `emacs -Q', setting `mouse-1-click-follows-link' = nil,
> > `mouse-2' gives the same error message, plus an additional error
> > saying that `symbol' is an bound variable.
> >
> > widget-button-click: Wrong type argument: consp, #<overlay from
> > 259 to 272 in *Customize Face: Dired Header*>
> > Symbol's value as variable is void: symbol
> 
> Strange, cus-edit.el does have lexical-binding, it should work.

My bad.  Sorry for the noise.

Adding a -*- lexical-binding:t -*- declaration to the patch-test
file I used makes it work - the link is followed OK, and there is
no void-var error.  (But I do still get the wrong-type-arg error.)