Use old Qt connect syntax for QTimer::singleShot

The new syntax is for Qt>=5.4 only, but we need to support back to Qt 5.2

src/widget/form/chatform.cpp

@@ -869,7 +869,7 @@ void ChatForm::onScreenshotClicked()
     doScreenshot();
     
     // Give the window manager a moment to open the fullscreen grabber window
-    QTimer::singleShot(500, this, &ChatForm::hideFileMenu);
+    QTimer::singleShot(500, this, SLOT(hideFileMenu()));
 }
 
 void ChatForm::doScreenshot()

src/widget/tool/flyoutoverlaywidget.cpp

@@ -109,7 +109,7 @@ void FlyoutOverlayWidget::finishedAnimation()
     
     // Delay it by a few frames to let the system catch up on rendering
     if (hide)
-        QTimer::singleShot(50, this, &FlyoutOverlayWidget::hidden);
+        QTimer::singleShot(50, this, SIGNAL(hidden()));
     
 }