bug#24073: 24.5; outline-on-heading-p sees any invisible text property as outline inviisble

[Eli Zaretskii]

> From: Paul Rankin <hello@paulwrankin.com>
> Date: Tue, 26 Jul 2016 19:29:18 +1000
> 
> A better solution is to make `outline-invisible-p' return t only if invisible 
> text property is `outline'
> 
>     (defsubst outline-invisible-p (&optional pos)
>       "Non-nil if the character after point is invisible."
>       (eq (get-char-property (or pos (point)) 'invisible)
>           'outline))

For outline's own use, sure.  But this function is also used by Org,
so I think we need to coordinate with Org developers about such a
change, to make sure we don't break Org in the process.

Btw, can you describe the real-life use case where you bumped into
this issue?

Thanks.