Changed the Windows gauard around so that it only works for VisualStudio

and not Cygwin/Mingw.

src/osg/Notify.cpp

@@ -28,7 +28,7 @@ bool osg::initNotifyLevel()
     g_NotifyInit = true;
 
     // set up global notify null stream for inline notify
-#if defined(WIN32) && !defined(__CYGWIN__)
+#if defined(WIN32) && !(defined(__CYGWIN__) || defined(__MINGW32__))
     g_NotifyNulStream = std::auto_ptr<ofstream>(osgNew std::ofstream ("nul"));
 #else
     g_NotifyNulStream.reset(osgNew std::ofstream ("/dev/null"));