Add backend support for suboridnate uids and gids

These files list the set of subordinate uids and gids that users are allowed
to use.   The expect use case is with the user namespace but other uses are
allowed.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

lib/getdef.c

@@ -81,6 +81,12 @@ static struct itemdef def_table[] = {
 	{"SHA_CRYPT_MAX_ROUNDS", NULL},
 	{"SHA_CRYPT_MIN_ROUNDS", NULL},
 #endif
+	{"SUB_GID_COUNT", NULL},
+	{"SUB_GID_MAX", NULL},
+	{"SUB_GID_MIN", NULL},
+	{"SUB_UID_COUNT", NULL},
+	{"SUB_UID_MAX", NULL},
+	{"SUB_UID_MIN", NULL},
 	{"SULOG_FILE", NULL},
 	{"SU_NAME", NULL},
 	{"SYS_GID_MAX", NULL},