Update from Gnulib

This incorporates:
2018-09-10 timespec: fix resolution confusion
2018-09-09 mktime: simplify in prep for glibc merge
2018-09-07 intprops: minor clarification of code
2018-09-06 stddef: Override max_align_t on NetBSD 8.0/x86
2018-09-06 fcntl: Fix F_DUPFD_CLOEXEC behaviour on Haiku
2018-09-06 strtoll, strtoull: Rely on limits-h module
2018-09-06 limits-h: Provide numerical limits macros
2018-09-06 fcntl: Don't access nonexistent optional argument
2018-09-02 mktime: fix unlikely race+overflow bug
2018-08-31 mktime, timegm: simplify glibc time64_t
2018-08-31 mktime, timegm: simplify merge to glibc
* build-aux/config.guess, build-aux/config.sub:
* lib/dtotimespec.c, lib/fcntl.c, lib/intprops.h:
* lib/limits.in.h, lib/mktime-internal.h, lib/mktime.c:
* lib/stat-time.h, lib/strtol.c, lib/timegm.c:
* lib/timespec-add.c, lib/timespec-sub.c, lib/timespec.h:
* lib/utimens.c, m4/limits-h.m4, m4/stddef_h.m4:
Copy from Gnulib.

build-aux/config.guess

@@ -2,7 +2,7 @@
 # Attempt to guess a canonical system name.
 #   Copyright 1992-2018 Free Software Foundation, Inc.
 
-timestamp='2018-08-02'
+timestamp='2018-08-29'
 
 # This file is free software; you can redistribute it and/or modify it
 # under the terms of the GNU General Public License as published by
@@ -838,7 +838,7 @@ EOF
     *:BSD/OS:*:*)
 	echo "$UNAME_MACHINE"-unknown-bsdi"$UNAME_RELEASE"
 	exit ;;
-    arm*:FreeBSD:*:*)
+    arm:FreeBSD:*:*)
 	UNAME_PROCESSOR=`uname -p`
 	set_cc_for_build
 	if echo __ARM_PCS_VFP | $CC_FOR_BUILD -E - 2>/dev/null \