Add "redirdev" redirection device

- create a new "redirdev" element for this purpose

tests/qemuxml2xmltest.c

@@ -189,6 +189,8 @@ mymain(void)
     DO_TEST("lease");
     DO_TEST("event_idx");
 
+    DO_TEST("usb-redir");
+
     /* These tests generate different XML */
     DO_TEST_DIFFERENT("balloon-device-auto");
     DO_TEST_DIFFERENT("channel-virtio-auto");