ios: implement Qt::WindowTransparentForInput

If the flag is set, report to UIKit that it should
continue searching for the touch target by returning
'NO' from [UIView pointInside:].

Change-Id: I723f64fd855284fa60d0be18b2535dfa61f31381
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@theqtcompany.com>

src/plugins/platforms/ios/quiview.mm

@@ -280,6 +280,12 @@
 
 // -------------------------------------------------------------------------
 
+-(BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event
+{
+    if (m_qioswindow->window()->flags() & Qt::WindowTransparentForInput)
+        return NO;
+    return [super pointInside:point withEvent:event];
+}
 
 - (void)updateTouchList:(NSSet *)touches withState:(Qt::TouchPointState)state
 {