add missing method in OSX

btgui/OpenGLWindow/MacOpenGLWindow.h

@@ -56,6 +56,10 @@ public:
     {
         m_keyboardCallback = keyboardCallback;
     }
+    btKeyboardCallback getKeyboardCallback()
+	{
+	return m_keyboardCallback;
+}
     
 	void setWheelCallback (btWheelCallback wheelCallback)
     {