First step towards separate userdata argument

docs/c-api/http.h/mg_connect_ws.md

docs/c-api/http.h/mg_connect_ws_opt.md

docs/c-api/http_client.h/mg_connect_http.md

docs/c-api/http_client.h/mg_connect_http_opt.md

docs/c-api/http_server.h/mg_file_upload_handler.md

docs/c-api/net.h/mg_add_sock.md

docs/c-api/net.h/mg_add_sock_opt.md

docs/c-api/net.h/mg_bind.md

docs/c-api/net.h/mg_bind_opt.md

docs/c-api/net.h/mg_broadcast.md

docs/c-api/net.h/mg_connect.md

docs/c-api/net.h/mg_connect_opt.md

docs/c-api/net.h/mg_event_handler_t.md

docs/c-api/net.h/mg_next.md

mongoose.c

mongoose.h