Clean up a lockfile from /tmp on exit. Fixes #4348

3rdparty/qtsingleapplication/qtlocalpeer.cpp

@@ -209,3 +209,8 @@ void QtLocalPeer::receiveConnection()
     emit messageReceived(uMsg); //### (might take a long time to return)
     emit messageReceived(QString::fromUtf8(uMsg));
 }
+
+QtLocalPeer::~QtLocalPeer ()
+{
+  lockFile.remove();
+}

3rdparty/qtsingleapplication/qtlocalpeer.h

@@ -57,6 +57,7 @@ class QtLocalPeer : public QObject
 
 public:
     QtLocalPeer(QObject *parent = 0, const QString &appId = QString());
+    ~QtLocalPeer ();
     bool isClient();
     bool sendMessage(const QString &message, int timeout);
     bool sendMessage(const QByteArray &message, int timeout);