bug#23730: 24.5; format removes text properties

[Eli Zaretskii]

> From: ynyaaa@gmail.com
> Cc: 23730@debbugs.gnu.org
> Date: Thu, 09 Jun 2016 11:07:01 +0900
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >The documentation only promises that the characters
> >_other_ than the format specifier are copied with their properties,
> 
> Text properties after the format spericifier are copied
> with wrong positions.
> 
> (format (concat (propertize "%2d" 'x 'X)
>                 (propertize "a" 'a 'A)
>                 (propertize "b" 'b 'B))
>         1)
> =>#(" 1ab" 0 1 (a A) 1 2 (b B))

Fixed on the master branch, thanks.  Fixing this also corrected your
originally reported issue, so I made it clear in the documentation
that the text properties from the format specifiers are also copied.