Update Gnulib to v0.1-4379-g2ef5a9b4b

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

lib/dynarray.h

@@ -0,0 +1,31 @@
+/* Type-safe arrays which grow dynamically.
+   Copyright 2021 Free Software Foundation, Inc.
+
+   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 3 of the License, 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 <https://www.gnu.org/licenses/>.  */
+
+/* Written by Paul Eggert, 2021.  */
+
+#ifndef _GL_DYNARRAY_H
+#define _GL_DYNARRAY_H
+
+#include <libc-config.h>
+
+#define __libc_dynarray_at_failure gl_dynarray_at_failure
+#define __libc_dynarray_emplace_enlarge gl_dynarray_emplace_enlarge
+#define __libc_dynarray_finalize gl_dynarray_finalize
+#define __libc_dynarray_resize_clear gl_dynarray_resize_clear
+#define __libc_dynarray_resize gl_dynarray_resize
+#include <malloc/dynarray.h>
+
+#endif /* _GL_DYNARRAY_H */