Header contains `signals' - use `Q_SIGNALS' instead!

Change-Id: I5ee1bfd0ce9c98d64b50cc727d414037fafb91c5
Reviewed-by: Rohan McGovern <rohan.mcgovern@nokia.com>

src/gui/kernel/qplatformscreenpageflipper.h

@@ -84,7 +84,7 @@ public:
 
     virtual bool displayBuffer(QPlatformScreenBuffer *) = 0;
 
-signals:
+Q_SIGNALS:
     void bufferDisplayed(QPlatformScreenBuffer *);
     void bufferReleased(QPlatformScreenBuffer *);
 };