Update Gnulib to v0.1-4379-g2ef5a9b4b

Also bump required autoconf version to 2.64, as required by Gnulib.

lib/flock.c

@@ -1,12 +1,12 @@
 /* Emulate flock on platforms that lack it, primarily Windows and MinGW.
 
    This is derived from sqlite3 sources.
-   http://www.sqlite.org/cvstrac/rlog?f=sqlite/src/os_win.c
-   http://www.sqlite.org/copyright.html
+   https://www.sqlite.org/src/finfo?name=src/os_win.c
+   https://www.sqlite.org/copyright.html
 
    Written by Richard W.M. Jones <rjones.at.redhat.com>
 
-   Copyright (C) 2008-2017 Free Software Foundation, Inc.
+   Copyright (C) 2008-2021 Free Software Foundation, Inc.
 
    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
@@ -19,12 +19,12 @@
    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/>.  */
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
 
 #include <config.h>
 #include <sys/file.h>
 
-#if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
+#if defined _WIN32 && ! defined __CYGWIN__
 
 /* LockFileEx */
 # define WIN32_LEAN_AND_MEAN
@@ -33,7 +33,11 @@
 # include <errno.h>
 
 /* _get_osfhandle */
-# include "msvc-nothrow.h"
+# if GNULIB_MSVC_NOTHROW
+#  include "msvc-nothrow.h"
+# else
+#  include <io.h>
+# endif
 
 /* Determine the current size of a file.  Because the other braindead
  * APIs we'll call need lower/upper 32 bit pairs, keep the file size