fix deprecated warning QTime::start()

Use
QElapsedTimer::QElapsedTimer()
instead.
This function was introduced in Qt 5.4.

SingleApplication/singleapplication.cpp

@@ -82,7 +82,7 @@ SingleApplication::SingleApplication( int &argc, char *argv[], bool allowSeconda
     }
 
     InstancesInfo* inst = static_cast<InstancesInfo*>( d->memory->data() );
-    QTime time;
+    QElapsedTimer time;
     time.start();
 
     // Make sure the shared memory block is initialised and in consistent state

SingleApplication/singleapplication.h

@@ -25,6 +25,7 @@
 
 #include <QtCore/QtGlobal>
 #include <QtNetwork/QLocalSocket>
+#include <QElapsedTimer>
 
 #ifndef QAPPLICATION_CLASS
   #define QAPPLICATION_CLASS QCoreApplication