Force Turkish locales back to C/POSIX; bz#2643

Turkish locales are unique in their handling of the letters 'i' and
'I' (yes, they are different letters) and OpenSSH isn't remotely
prepared to deal with that. For now, the best we can do is to force
OpenSSH to use the C/POSIX locale and try to preserve the UTF-8
encoding if possible.

ok dtucker@
diff --git a/utf8.h b/utf8.h
index 43ce1d5..88c5a34 100644
--- a/utf8.h
+++ b/utf8.h
@@ -22,3 +22,4 @@
 int	 vfmprintf(FILE *, const char *, va_list);
 int	 snmprintf(char *, size_t, int *, const char *, ...)
 	     __attribute__((format(printf, 4, 5)));
+void	 msetlocale(void);