when SerialStream was dropped, the member "inner: mem::ManuallyDrop<serialport::COMPort>" was not dropped, this will prevent to open the serial again.  in the code: examples\read_serialport.rs  
when SerialStream was dropped, the member "inner: mem::ManuallyDropserialport::COMPort" was not dropped, this will prevent to open the serial again.
in the code: examples\read_serialport.rs