bug#31552: 27.0.50; Document that Emacs in batch mode exits with exit status -1 on error

[Eli Zaretskii]

> From: Philipp <p.stephani2@gmail.com>
> Date: Tue, 22 May 2018 15:41:25 +0200
> 
> I haven't found any documentation in the Lisp reference manual that the
> exit status of an Emacs process exiting due to a nonlocal exit is -1 by
> default (adjusted to 255 by Bash).  This should be documented, for users
> that run Emacs in batch mode.

I'm not sure I understand what you are describing.  Can you show a
reproducer?

Thanks.