Fix release mode warnings about unused variables.

Variables that are only used in asserts.

Change-Id: I0984b676ad9b67f5ae72266b8540e8054163918f
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>

src/corelib/thread/qthread_win.cpp

@@ -238,6 +238,7 @@ DWORD WINAPI qt_adopted_thread_watcher_function(LPVOID)
                 QThread *thread = data->thread;
                 Q_ASSERT(thread);
                 QThreadPrivate *thread_p = static_cast<QThreadPrivate *>(QObjectPrivate::get(thread));
+                Q_UNUSED(thread_p)
                 Q_ASSERT(!thread_p->finished);
                 thread_p->finish(thread);
             }

src/gui/kernel/qplatformintegration_qpa.cpp

@@ -247,6 +247,7 @@ QPlatformSharedGraphicsCache *QPlatformIntegration::createPlatformSharedGraphics
 */
 QPaintEngine *QPlatformIntegration::createImagePaintEngine(QPaintDevice *paintDevice) const
 {
+    Q_UNUSED(paintDevice)
     return 0;
 }
 

src/gui/painting/qpainter.cpp

@@ -7270,6 +7270,7 @@ void QPainter::setRedirected(const QPaintDevice *device,
                              const QPoint &offset)
 {
     Q_ASSERT(device != 0);
+    Q_UNUSED(device)
     Q_UNUSED(replacement)
     Q_UNUSED(offset)
     qWarning("QPainter::setRedirected(): ignoring call to deprecated function, use QWidget::render() instead");