Skip nested procedures in .async. macro

Fixes #3075

tests/async/t3075.nim

@@ -0,0 +1,29 @@
+import asyncnet, asyncdispatch, strtabs
+
+type
+  WebSocketCallback = proc (client: WebSocket, message: WebSocketMessage) {.closure, gcsafe.}
+  WebSocketRecvClosure = proc (ws: WebSocket): Future[string] {.gcsafe.}
+
+  WebSocketMessage = ref object
+    msg: string
+
+  WebSocket = ref object
+    socket:     AsyncSocket
+    header:     StringTableRef
+    onOpen:     WebSocketCallback
+    onMessage:  WebSocketCallback
+    onClose:    WebSocketCallback
+
+proc recv(ws: WebSocket, p: WebSocketRecvClosure): Future[string] {.async.}=
+  if not ws.socket.isClosed():
+    result = await ws.p()
+    if result == "":
+      ws.socket.close()
+      if ws.onClose != nil:
+        ws.onClose(ws, nil)
+  return result
+
+proc reсvSize(ws: WebSocket, size: int): Future[string] {.async.} =
+  proc recvSizeClosure(ws: WebSocket): Future[string] {.async.} =
+    return await ws.socket.recv(size)
+  return await ws.recv(recvSizeClosure)