Close the handle for the events that were created

The handles should be closed when QSerialPort is deleted in order to clean
up the native resources.

Change-Id: If04521fc0fa3b898093bda3317962b4c44818034
Reviewed-by: Denis Shienkov <denis.shienkov@gmail.com>
Reviewed-by: Sergey Belyashov <Sergey.Belyashov@gmail.com>

src/serialport/qserialport_win.cpp

@@ -127,6 +127,16 @@ QSerialPortPrivate::QSerialPortPrivate(QSerialPort *q)
     }
 }
 
+QSerialPortPrivate::~QSerialPortPrivate()
+{
+    if (communicationOverlapped.hEvent)
+        CloseHandle(communicationOverlapped.hEvent);
+    if (readCompletionOverlapped.hEvent)
+        CloseHandle(readCompletionOverlapped.hEvent);
+    if (writeCompletionOverlapped.hEvent)
+        CloseHandle(writeCompletionOverlapped.hEvent);
+}
+
 bool QSerialPortPrivate::open(QIODevice::OpenMode mode)
 {
     Q_Q(QSerialPort);

src/serialport/qserialport_win_p.h

@@ -63,6 +63,7 @@ class QSerialPortPrivate : public QSerialPortPrivateData
 
 public:
     QSerialPortPrivate(QSerialPort *q);
+    ~QSerialPortPrivate();
 
     bool open(QIODevice::OpenMode mode);
     void close();