gabble_call_stream_dispose: use tp_clear_object, tp_clear_pointer
gabble_call_stream_dispose: use tp_clear_object, tp_clear_pointer

mlundblad/telepathy-gabble,Ziemin/telepathy-gabble,mlundblad/telepathy-gabble,jku/telepathy-gabble,mlundblad/telepathy-gabble,jku/telepathy-gabble,Ziemin/telepathy-gabble,jku/telepathy-gabble,Ziemin/telepathy-gabble,Ziemin/telepathy-gabble