bug#20258: 24.5; format-time-string miscounting of multibyte characters

[Eli Zaretskii]

> From: Gunnar Horrigmo <gunnar.horrigmo@usit.uio.no>
> Date: Sat, 04 Apr 2015 16:33:50 +0200
> 
> 
> As the subject says, format-time-string miscounts multibyte characters.
> Simple example with nb_NO.utf8 locale, where ø is two bytes:
> 
> (format-time-string "%6a" (date-to-time "Sat Apr  4 16:14:40 2015"))
> "  lø."
> 
> (length (format-time-string "%6a" (date-to-time "Sat Apr  4 16:14:40 2015")))
> 5

'length' counts characters, not bytes.  If you need to count bytes,
use 'string-bytes' instead:

  (string-bytes "  lø.") => 6