udevng: hook up legacy devices

...and disable old udev code by shorting it out in it's init() function.

The check_device function is augmented to differentiate between USB
and serial devices:

- if the device sits on a USB bus, the device is handled as before
- if not, an attempt is made to handle the device as a serial device

plugins/udev.c

@@ -365,6 +365,8 @@ static void udev_start(void)
 
 static int udev_init(void)
 {
+	return 0;
+
 	devpath_list = g_hash_table_new_full(g_str_hash, g_str_equal,
 						g_free, g_free);
 	if (devpath_list == NULL) {

plugins/udevng.c

@@ -1562,6 +1562,9 @@ static void check_device(struct udev_device *device)
 	if ((g_str_equal(bus, "usb") == TRUE) ||
 			(g_str_equal(bus, "usbmisc") == TRUE))
 		check_usb_device(device);
+	else
+		add_serial_device(device);
+
 }
 
 static gboolean create_modem(gpointer key, gpointer value, gpointer user_data)