Added one-second delay when switching between programmer and bootloader.

Just makes me feel better to ensure the "OK" confirmation arrives at the
computer.

usb_serial/usb_serial.c

@@ -167,6 +167,10 @@ void USBSerial_HandleWaitingForCommandByte(uint8_t byte)
 	// Enter the bootloader. Wait a bit, then jump to the bootloader location.
 	case EnterBootloader:
 		SendByte(CommandReplyOK);
+		CDC_Device_Flush(&VirtualSerial_CDC_Interface);
+
+		// Insert a small delay to ensure that it arrives before rebooting.
+		_delay_ms(1000);
 
 		// Done with the USB interface -- the bootloader will re-initialize it.
 		USB_Disable();