Support for X-VERSION command

+/* GNU mailutils - a suite of utilities for electronic mail
+   Copyright (C) 1999, 2001 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
+   the Free Software Foundation; either version 2, 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */
+
+#include "imap4d.h"
+
+int
+imap4d_version (struct imap4d_command *command, char *arg)
+{
+  util_send ("* %s GNU %s\r\n", command->name, argp_program_version);
+  return util_finish (command, RESP_OK, "Completed");
+}