Mac: Don't register for Pan Gestures.

This will enable touch events for the viewport
widget, which has undesired side effects (see task).

Fixes a regression from Qt 4.

Task-number: QTBUG-38815
Change-Id: I7b9c0d1de985d1c82f946140fecf460fcfc5e686
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>

src/widgets/widgets/qabstractscrollarea.cpp

@@ -309,7 +309,7 @@ void QAbstractScrollAreaPrivate::init()
     q->setFrameStyle(QFrame::StyledPanel | QFrame::Sunken);
     q->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
     layoutChildren();
-#ifndef Q_WS_MAC
+#ifndef Q_OS_OSX
 #  ifndef QT_NO_GESTURES
     viewport->grabGesture(Qt::PanGesture);
 #  endif