Org-reveal: Double prefix arg show the entire subtree of the parent

Org-reveal: Double prefix arg show the entire subtree of the parent

This can help to get out of an inconsistent state produce for example
by viewing from the agenda.  Reported by Matt Lundin:

> I'd like to report a minor issue with org-agenda-goto and inline tasks.
> Let's say one has the following file:
>
> --8<---------------cut here---------------start------------->8---
> * Here is an entry.
> Blah blah blah blah.
> *************** Here is an inline task.
> *************** END
> Blah blah blah blah blah.
> *************** TODO Here is a second inline task.
> *************** END
> Blah blah blah blah blah.
> *************** Here is a third inline task
> *************** END
> Blah blah blah blah blah.
> --8<---------------cut here---------------end--------------->8---
>
> Let's say one also has the following settings:
>
> --8<---------------cut here---------------start------------->8---
> (setq org-show-hierarchy-above t)
> (setq org-show-siblings '((default . nil) (isearch . t) (agenda . t)))
> (setq org-show-entry-below '((default . nil) (isearch . t) (agenda . t)))
> --8<---------------cut here---------------end--------------->8---
>
> If 1) one tries to jump to the TODO from the agenda and 2) the entry is
> currently folded, org-show-context reveals only the headlines. E.g.,
>
> --8<---------------cut here---------------start------------->8---
> * Here is an entry.
> *************** Here is an inline task.
> *************** END...
> *************** TODO Here is a second inline task.
> *************** END...
> *************** Here is a third inline task
> *************** END...
> --8<---------------cut here---------------end--------------->8---
>
> Invoking org-cycle on the END headline does nothing, since all headlines
> deeper than org-inlinetask-min-level are exempted from cycling. As a
> result, the only way to reveal the text in the entry is to cycle the
> parent twice (first to close, then to reveal).