4 new functions to retrieve single linked list of group and passwd entries

+ a fix to an infinite loop in srv_samr_nt.c caused by misuse of
setgrent/getgrent/endgrent solved by these new functions

source/include/util_getent.h

@@ -0,0 +1,45 @@
+/*
+   Unix SMB/Netbios implementation.
+   Version 3.0
+   Samba utility functions
+   Copyright (C) Simo Sorce 2001
+
+   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 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 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.
+*/
+
+/* element for a single linked list of group entries */
+/* replace the use of struct group in some cases */
+/* used by getgrent_list() */
+struct sys_grent {
+	char *gr_name;
+	char *gr_passwd;
+	gid_t gr_gid;
+	char **gr_mem;
+	struct sys_grent *next;
+};
+
+/* element for a single linked list of passwd entries */
+/* replace the use of struct passwd in some cases */
+/* used by getpwent_list() */
+struct sys_pwent {
+	char *pw_name;
+	char *pw_passwd;
+	uid_t pw_uid;
+	gid_t pw_gid;
+	char *pw_gecos;
+	char *pw_dir;
+	char *pw_shell;
+	struct sys_pwent *next;
+};