It seems the package is no more included in the extensions plug-in package however ProfilesEngineExtendedAPI.ZIP is present.
It was included in the previous extensions plug-in packages for S60 3rd Edition.
The headers are not available in the SDK S60 3rd Edition FP1.
So it is not possible to use CProfileChangeNotifyHandler.h and MProfileChangeObserver.h mentioned in the Forum Nokia Wiki.