Function switch_rtp_dequeue_dtmf 

pub unsafe extern "C" fn switch_rtp_dequeue_dtmf(
    rtp_session: *mut switch_rtp_t,
    dtmf: *mut switch_dtmf_t,
) -> switch_size_t

\brief Retrieve DTMF digits from a given RTP session \param rtp_session RTP session to retrieve digits from \param dtmf the dtmf \return number of bytes read into the buffer