Add intercept_authenticate sudoers option, defaults to false.

By default, sudoers will not require authentication of commands run
via an intercepted session.  To require authenticaton of subsequent
commands, enable intercept_authenticate in sudoers.

plugins/sudoers/def_data.c

@@ -589,6 +589,10 @@ struct sudo_defs_types sudo_defs_table[] = {
 	"log_exit_status", T_FLAG,
 	N_("Log the exit status of commands"),
 	NULL,
+    }, {
+	"intercept_authenticate", T_FLAG,
+	N_("Subsequent commands in an intercepted session must be authenticated"),
+	NULL,
     }, {
 	NULL, 0, NULL
     }