Removed the obsolete aio module.

src/core/ngx_resolver.c

diff --git a/src/core/ngx_resolver.c b/src/core/ngx_resolver.c
index 4e9c85d..d863b4c 100644
--- a/src/core/ngx_resolver.c
+++ b/src/core/ngx_resolver.c
@@ -3092,7 +3092,7 @@
 
     rc = connect(s, uc->sockaddr, uc->socklen);
 
-    /* TODO: aio, iocp */
+    /* TODO: iocp */
 
     if (rc == -1) {
         ngx_log_error(NGX_LOG_CRIT, &uc->log, ngx_socket_errno,