fix Qt4 QSocketNotifier configure check

When built as a part of the configure check, this doesn't know SAL_OVERRIDE.

Change-Id: I1420dd50efdd6666f246884f286a3f29e0b56a2c

vcl/unx/kde4/tst_exclude_socket_notifiers.hxx

@@ -28,6 +28,11 @@
 #include <QtNetwork/qtcpserver.h>
 #include <QtNetwork/qtcpsocket.h>
 
+// This is also used by a configure check.
+#ifndef SAL_OVERRIDE
+#define SAL_OVERRIDE
+#endif
+
 class SocketEventsTester: public QObject
 {
     Q_OBJECT