QmlDesigner: fixing compile for Qt 5

grabMouseWhileInWindow(); is not an
option in Qt 5 anymore.

Change-Id: Ie198a0e3d83fffb62ff51ec2475134cdf4f9dcee
Reviewed-by: Marco Bubke <marco.bubke@digia.com>
(cherry picked from commit cda0c6c3)

src/plugins/qmldesigner/components/itemlibrary/customdraganddrop.cpp

@@ -39,7 +39,7 @@
 #include <QDebug>
 #include <QPainter>
 
-#ifdef Q_OS_WIN
+#if defined(Q_OS_WIN) && QT_VERSION < 0x050000
 #include <private/qwidget_p.h>
 #endif
 
@@ -64,7 +64,7 @@ void CustomDragAndDropIcon::startDrag()
 
 void CustomDragAndDropIcon::grabMouseSafely()
 {
-#ifdef Q_OS_WIN
+#if defined(Q_OS_WIN) && QT_VERSION < 0x050000
     // grabMouse calls SetWindowsHookEx() - this function causes a system-wide
     // freeze if any other app on the system installs a hook and fails to
     // process events.