Add a version number field to the jail(2) argument so that future changes

can be handled intelligently.

WARNING:  you will need to reinstall #includes and recompile jail(8).

usr.sbin/jail/jail.c

@@ -29,6 +29,8 @@ main(int argc, char **argv)
 	i = chdir(argv[1]);
 	if (i)
 		err(1, "chdir %s", argv[1]);
+	memset(&j, 0, sizeof(j));
+	j.version = 0;
 	j.path = argv[1];
 	j.hostname = argv[2];
 	i = inet_aton(argv[3], &in);