win: fix compilation warning

-Wdeclaration-after-statement

PR-URL: https://github.com/libuv/libuv/pull/990
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

src/win/async.c

@@ -69,12 +69,12 @@ int uv_async_send(uv_async_t* handle) {
 
 void uv_process_async_wakeup_req(uv_loop_t* loop,
                                  uv_req_t* req) {
-  assert(req->type == UV_WAKEUP);
-
   QUEUE queue;
   QUEUE* q;
   uv_async_t* h;
 
+  assert(req->type == UV_WAKEUP);
+
   QUEUE_MOVE(&loop->async_handles, &queue);
   while (!QUEUE_EMPTY(&queue)) {
     q = QUEUE_HEAD(&queue);