Added GUIEventHandler to allow one to write out models with event callbacks

src/osgWrappers/serializers/osgGA/GUIEventHandler.cpp

@@ -0,0 +1,11 @@
+#include <osgGA/GUIEventHandler>
+#include <osgDB/ObjectWrapper>
+#include <osgDB/InputStream>
+#include <osgDB/OutputStream>
+
+REGISTER_OBJECT_WRAPPER( osgGA_GUIEventHandler,
+                         new osgGA::GUIEventHandler,
+                         osgGA::GUIEventHandler,
+                         "osg::Object osgGA::GUIEventHandler" )
+{
+}