ws2_32/tests: Test AcceptEx during pending AcceptEx call.

dlls/ws2_32/tests/sock.c

@@ -2774,6 +2774,11 @@ static void test_AcceptEx(void)
         &bytesReturned, &overlapped);
     ok(bret == FALSE && WSAGetLastError() == ERROR_IO_PENDING, "AcceptEx returned %d + errno %d\n", bret, WSAGetLastError());
 
+    bret = pAcceptEx(listener, acceptor, buffer, 0,
+        sizeof(struct sockaddr_in) + 16, sizeof(struct sockaddr_in) + 16,
+        &bytesReturned, &overlapped);
+    ok(bret == FALSE && WSAGetLastError() == WSAEINVAL, "AcceptEx on already pending socket returned %d + errno %d\n", bret, WSAGetLastError());
+
     iret = connect(connector, (struct sockaddr*)&bindAddress, sizeof(bindAddress));
     ok(iret == 0, "connecting to accepting socket failed, error %d\n", WSAGetLastError());