Added KeyboardMouseCallback::shutdown() support.

include/osgProducer/KeyboardMouseCallback

@@ -54,6 +54,8 @@ class OSGPRODUCER_EXPORT KeyboardMouseCallback : public Producer::KeyboardMouseC
 
 	virtual void specialKeyPress( Producer::KeyCharacter key);
 	virtual void specialKeyRelease( Producer::KeyCharacter key);
+        
+        virtual void shutdown();
 
 
         void setEscapeSetDone(bool esc) { _escapeKeySetsDone = esc; }

src/osgProducer/KeyboardMouseCallback.cpp

@@ -203,3 +203,9 @@ EventAdapter* KeyboardMouseCallback::createEventAdapter()
     
     return ea;
 }
+
+void KeyboardMouseCallback::shutdown()
+{
+    _done = true;
+    _keyboardMouse->cancel();
+}