* Added the ability to change screen modes on the fly. This works both in OpenGL and SDL modes. * Added IEngineChangeListener so the client can update the cameras viewport if the screen mode has been changed. I chose to do it this way because the engine has no way to know which camera it should update. It will be up to the client to do it. * The cursor surface is now correctly freed when exiting. * Added DeviceCaps::getNearestScreenMode() for the client to request a supported screen mode. closes[t:315]