windows: initialize ares handles list

We need to initialize the ares handles linked list or else bad things can happen
when we try to perform async lookups.

src/win/core.c

@@ -59,6 +59,7 @@ static void uv_init(void) {
 
 
 static void uv_loop_init(uv_loop_t* loop) {
+  loop->uv_ares_handles_ = NULL;
   /* Create an I/O completion port */
   loop->iocp = CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, 0, 1);
   if (loop->iocp == NULL) {