msg: always ignore frame->is_relevant if f_handl->is_relevant is known
msg.h: move frame iteration stuff to facilitate later rebasing
hna: declare tun6 description_msg_tun6..._adv as is_relevant=0
sms: rename json_sms -> sms_node
hna: check for overlapping hna announcements or FAILURE
purge niit
bmx msg: assert on->desc if on->added
elastic compatibility version (cv) field in packet header and description, other cv16-compatible description changes
bmx msg: packet_header changes ignoring pkt_sqn and towards uint64_t local_id for CV18
msg bmx hna: purge tlv_hashes, fix get_desc_frame_data(), desc_frame_changed() process_description_tlvs_del() rx_frame_iterate()