maint: update to latest gnulib

This pulls in updates for the 2018 copyright year, among other things.
Signed-off-by: NEric Blake <eblake@redhat.com>

.gnulib @ 7e7c5c79

-Subproject commit 5e9abf87163ad4aeaefef0b02961f8674b0a4879
+Subproject commit 7e7c5c7952b7de1e33c8eba891cc425d5d8d7803

bootstrap

@@ -4,7 +4,7 @@ scriptversion=2017-09-19.08; # UTC
 
 # Bootstrap this package from checked-out sources.
 
-# Copyright (C) 2003-2017 Free Software Foundation, Inc.
+# Copyright (C) 2003-2018 Free Software Foundation, Inc.
 
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -792,7 +792,7 @@ symlink_to_dir()
       # aren't confused into doing unnecessary builds.  Conversely, if the
       # existing symlink's timestamp is older than the source, make it afresh,
       # so that broken tools aren't confused into skipping needed builds.  See
-      # <https://lists.gnu.org/archive/html/bug-gnulib/2011-05/msg00326.html>.
+      # <https://lists.gnu.org/r/bug-gnulib/2011-05/msg00326.html>.
       test -h "$dst" &&
       src_ls=$(ls -diL "$src" 2>/dev/null) && set $src_ls && src_i=$1 &&
       dst_ls=$(ls -diL "$dst" 2>/dev/null) && set $dst_ls && dst_i=$1 &&