bug#8545: issues with recent doprnt-related changes

[Eli Zaretskii]

> Date: Fri, 29 Apr 2011 08:28:35 -0400
> From: Richard Stallman <rms@gnu.org>
> Cc: lekktu@gmail.com, 8545@debbugs.gnu.org
> 
>     No, format_end is already pointing after the object;
>     the object's size is format_end - format.  So
>     format_end + 1 might not be a valid pointer.
> 
> 20 years ago, Emacs allocated an extra byte with a null character
> after the end of every string or buffer.

20 years later, we still do that for strings, but (AFAICS) not for
buffers.