tcp_in: Flag the pcb as closing if TCP_EVENT_CLOSED refused

Closes https://github.com/espressif/esp-lwip/issues/18

src/core/tcp_in.c

@@ -541,6 +541,10 @@ tcp_input(struct pbuf *p, struct netif *inp)
             TCP_EVENT_CLOSED(pcb, err);
             if (err == ERR_ABRT) {
               goto aborted;
+#if ESP_LWIP
+            } else if (err == ERR_MEM) {
+                tcp_set_flags(pcb, TF_CLOSEPEND);
+#endif /* ESP_LWIP */
             }
           }
         }