res_usbradio: Add ability to specify allowed vid:pid

This updates res_usbradio to allow users to specify USB device descriptor(s) that can be used for interface devices. There are compatible chips that are not supported in the code. This will allow users to easily add the compatible chip(s).

This adds res_usbradio.conf for configuration. A sample configuration file was added.

Reworked the supported/known USB devices lookup. The supported devices are now in an array.

This closes #359.

res/res_usbradio.c

@@ -939,7 +939,7 @@ static int load_config(int reload)
 				}
 				device->idVendor = idVendor;
 				device->idProduct = idProduct;
-				device->idMask = 0xfff;
+				device->idMask = 0xffff;
 				/* Add it to our list */
 				AST_RWLIST_WRLOCK(&user_devices);
 				AST_LIST_INSERT_HEAD(&user_devices, device, entry);