Don't parse %s format argument as multibyte string

2012-09-28  Andreas Schwab  <schwab@linux-m68k.org>

            [BZ #6530]
            * stdio-common/vfprintf.c (process_string_arg): Revert
            2000-07-22 change.

2011-09-28  Jonathan Nieder  <jrnieder@gmail.com>

            * stdio-common/Makefile (tst-sprintf-ENV): Set environment
            for testcase.
            * stdio-common/tst-sprintf.c: Include <locale.h>
            (main): Test sprintf's handling of incomplete multibyte
            characters.

(cherry picked from commit 715a900c)