Fix etcp_socket_add to register sockets with uasync

src/etcp_connections.c

@@ -13,6 +13,8 @@
 #include "../lib/memory_pool.h"
 #include "../lib/u_async.h"
 #include <stdlib.h>
+static void etcp_connections_read_callback(int fd, void* arg);
+
 #include <time.h>
 
 // Simple debug macros to replace missing debug_config.h