Update Gnulib to 6835fc458f30b94f15d69c35a79cbc2dfabe2d06.

lib/timegm.c

@@ -0,0 +1,40 @@
+/* Convert UTC calendar time to simple time.  Like mktime but assumes UTC.
+
+   Copyright (C) 1994, 1997, 2003-2004, 2006-2007, 2009-2016 Free Software
+   Foundation, Inc.  This file is part of the GNU C Library.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU Lesser General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public License
+   along with this program; if not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef _LIBC
+# include <config.h>
+#endif
+
+#include <time.h>
+
+#ifdef _LIBC
+typedef time_t mktime_offset_t;
+#else
+# undef __gmtime_r
+# define __gmtime_r gmtime_r
+# define __mktime_internal mktime_internal
+# include "mktime-internal.h"
+#endif
+
+time_t
+timegm (struct tm *tmp)
+{
+  static mktime_offset_t gmtime_offset;
+  tmp->tm_isdst = 0;
+  return __mktime_internal (tmp, __gmtime_r, &gmtime_offset);
+}