Partially modified to use C++11 standard nullptr

Change-Id: Ibfd76357ceb56b347afe7122fc252b866b21cb11
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

src/widgets/kernel/qmacgesturerecognizer.cpp

@@ -179,7 +179,7 @@ QGesture *QMacPanGestureRecognizer::create(QObject *target)
         w->setAttribute(Qt::WA_TouchPadAcceptSingleTouchEvents);
         return new QPanGesture;
     }
-    return 0;
+    return nullptr;
 }
 
 void QMacPanGestureRecognizer::timerEvent(QTimerEvent *ev)

src/widgets/kernel/qwidget.cpp

@@ -11977,7 +11977,7 @@ void QWidgetPrivate::adjustQuitOnCloseAttribute()
 QOpenGLContext *QWidgetPrivate::shareContext() const
 {
 #ifdef QT_NO_OPENGL
-    return 0;
+    return nullptr;
 #else
     if (!extra || !extra->topextra || !extra->topextra->window)
         return nullptr;

src/widgets/widgets/qmdisubwindow.cpp

@@ -767,7 +767,7 @@ ControlContainer::~ControlContainer()
 QMenuBar *QMdiSubWindowPrivate::menuBar() const
 {
 #if !QT_CONFIG(mainwindow)
-    return 0;
+    return nullptr;
 #else
     Q_Q(const QMdiSubWindow);
     if (!q->isMaximized() || drawTitleBarWhenMaximized() || isChildOfTabbedQMdiArea(q))

src/widgets/widgets/qpushbutton_p.h

@@ -83,7 +83,7 @@ public:
 #if QT_CONFIG(dialog)
     QDialog *dialogParent() const;
 #else
-    QDialog *dialogParent() const { return 0; }
+    QDialog *dialogParent() const { return nullptr; }
 #endif
 
     QPointer<QMenu> menu;