Added osgGA::Device class for integration of both physical and virtual devices.

Added template readFile(..) function to make it more convinient to cast to a specific object type.

Added support for osgGA::Device to osgViewer.

Added sdl plugin to provides very basic joystick osgGA::Device integration.

include/osgGA/Device

@@ -0,0 +1,52 @@
+/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 Robert Osfield
+ *
+ * This library is open source and may be redistributed and/or modified under
+ * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or
+ * (at your option) any later version.  The full license is in LICENSE file
+ * included with this distribution, and on the openscenegraph.org website.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * OpenSceneGraph Public License for more details.
+*/
+
+#ifndef OSGGA_EVENTSOURCE
+#define OSGGA_EVENTSOURCE 1
+
+#include <osgGA/EventQueue>
+
+namespace osgGA {
+
+/**
+ * Device base class from abstracting away from devices/windows that can generate events.
+ */
+class OSGGA_EXPORT Device : public osg::Object
+{
+    public:
+
+        Device();
+        Device(const Device& es, const osg::CopyOp& copyop);
+
+        META_Object(osgGA,Device);
+
+        virtual void checkEvents() {};
+
+        void setEventQueue(osgGA::EventQueue* eventQueue) { _eventQueue = eventQueue; }
+        osgGA::EventQueue* getEventQueue() { return _eventQueue.get(); }
+        const osgGA::EventQueue* getEventQueue() const { return _eventQueue.get(); }
+
+    protected:
+
+        virtual ~Device();
+
+        /** Prevent unwanted copy operator.*/
+        Device& operator = (const Device&) { return *this; }
+
+        osg::ref_ptr<osgGA::EventQueue> _eventQueue;
+        
+};
+
+}
+
+#endif