Update from Gnulib by running admin/merge-gnulib

* lib/dirent-private.h, m4/codeset.m4, m4/locale-fr.m4, m4/musl.m4:
New files, from Gnulib.

lib/dirent-private.h

@@ -0,0 +1,67 @@
+/* Private details of the DIR type.
+   Copyright (C) 2011-2023 Free Software Foundation, Inc.
+
+   This file 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 2.1 of the
+   License, or (at your option) any later version.
+
+   This file 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/>.  */
+
+#ifndef _DIRENT_PRIVATE_H
+#define _DIRENT_PRIVATE_H 1
+
+#if HAVE_DIRENT_H                       /* mingw */
+
+# undef DIR
+
+struct gl_directory
+{
+  /* File descriptor to close during closedir().
+     Needed for implementing fdopendir().  */
+  int fd_to_close;
+  /* Pointer to the real DIR.  */
+  DIR *real_dirp;
+};
+
+/* Restore definition from dirent.h.  */
+# define DIR struct gl_directory
+
+#else                                   /* MSVC */
+
+# define WIN32_LEAN_AND_MEAN
+# include <windows.h>
+
+/* Don't assume that UNICODE is not defined.  */
+# undef WIN32_FIND_DATA
+# define WIN32_FIND_DATA WIN32_FIND_DATAA
+
+struct gl_directory
+{
+  /* File descriptor to close during closedir().
+     Needed for implementing fdopendir().  */
+  int fd_to_close;
+  /* Status, or error code to produce in next readdir() call.
+     -2 means the end of the directory is already reached,
+     -1 means the entry was already filled by FindFirstFile,
+     0 means the entry needs to be filled using FindNextFile.
+     A positive value is an error code.  */
+  int status;
+  /* Handle, reading the directory, at current position.  */
+  HANDLE current;
+  /* Found directory entry.  */
+  WIN32_FIND_DATA entry;
+  /* Argument to pass to FindFirstFile.  It consists of the absolutized
+     directory name, followed by a directory separator and the wildcards.  */
+  char dir_name_mask[1];
+};
+
+#endif
+
+#endif /* _DIRENT_PRIVATE_H */