Fixed CDC demo not sending an empty packet after each transfer to prevent the host from buffering incomming data.

Altered Project and Bootloader makefiles so that the path to the LUFA library can be set in one place.

Demos/Device/CDC/CDC.c

@@ -308,6 +308,12 @@ TASK(CDC_Task)
 		
 		/* Finalize the stream transfer to send the last packet */
 		Endpoint_ClearCurrentBank();
+
+		/* Wait until the endpoint is ready for another packet */
+		while (!(Endpoint_ReadWriteAllowed()));
+		
+		/* Send an empty packet to ensure that the host does not buffer data sent to it */
+		Endpoint_ClearCurrentBank();
 	}
 
 	/* Select the Serial Rx Endpoint */