lwIP 2.1.0 Lightweight IP stack

### - s -

- sd : api_msg
- select_waiting : lwip_sock
- sem : dns_api_msg , lwip_select_cb
- sem_signalled : lwip_select_cb
- send_timeout : netconn
- sendevent : lwip_sock
- sent_num : autoip
- sequence_number : ieee_802154_hdr
- service : mdns_service
- services : mdns_host
- session_data_packet_size : netbios_answer
- set_test : snmp_node_instance , snmp_table_node
- set_value : snmp_node_instance , snmp_table_node
- size : memp_desc
- socket : netconn
- source_addr : mdns_packet
- source_address : ieee_802154_hdr
- source_pan_id : ieee_802154_hdr
- src : ip6_hdr
- state : autoip , netconn , netif , netif_ext_callback_args_t::link_changed_s , netif_ext_callback_args_t::status_changed_s , smtp_session
- static_data : smtp_send_request
- stats : memp_desc
- status_callback : netif
- subject : smtp_session
- subject_len : smtp_session
- sys : stats_