Use of strftime in movemail.ec

[Eli Zaretskii]

movemail.c uses strftime as follows:

  char fromline[100];
  if (! strftime (fromline, sizeof fromline,
                  "From movemail %a %b %e %T %Y\n", ltime))

The %e and %T formats are not supported by the MS-Windows runtime
version of strftime, and the result is that movemail produces mbox
files where Rmail doesn't see any valid email messages.

I believe these format specifiers were used under the assumption that
Gnulib's strftime will be used on systems that don't support the full
functionality.  However, Gnulib's strftime.c defines a function
my_strftime, which is renamed by config.h as nstrftime, and I don't
see anywhere any machinery to force movemail call nstrftime.  Am I
missing something?

For now, I pushed a change to emacs-25 (commit 7923112) to use only
portable specifiers there.  But if a simple and safe change can be
made that would cause nstrftime be called by movemail (without any
adverse effects on Emacs itself), let's do that instead.