bug#9981: 24.0.91; mismatch in doc for `buffer-visibility-spec'

[Drew Adams]

> > But the doc string says this:
> >
> >  "a text character is invisible if its `invisible' property is an
> >   element in that list (or is a list with members in common)."
> 
> That symbol no longer seems to exist.

There is a typo in the subject line.  It is `buffer-invisibility-spec'.
                                                    ^^

> Closing.  If this is still
> relevant for some other symbol, please reopen.

Sorry.  Glenn has apparently blocked me from reopening bugs.