iOS: Disable drag and drop completely instead of enabling simple d'n'd

The drag and drop event filters do not play nicely with touch events
or virtual keyboards.

Task-number: QTBUG-35348
Change-Id: Id4d079ae72882f48750d394f13e10700d60e4532
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@digia.com>

src/plugins/platforms/ios/qiosintegration.h

@@ -74,6 +74,8 @@ public:
     QStringList themeNames() const;
     QPlatformTheme *createPlatformTheme(const QString &name) const;
 
+    QPlatformDrag *drag() const Q_DECL_OVERRIDE { return 0; }
+
     QAbstractEventDispatcher *createEventDispatcher() const;
     QPlatformNativeInterface *nativeInterface() const;