Close async socket on error (instead of looping on epoll_wait with 100% CPU)

lib/pure/asyncdispatch.nim

@@ -878,6 +878,10 @@ else:
       let data = PData(info.key.data)
       assert data.fd == info.key.fd.TAsyncFD
       #echo("In poll ", data.fd.cint)
+      if EvError in info.events:
+        closeSocket(data.fd)
+        continue
+
       if EvRead in info.events:
         # Callback may add items to ``data.readCBs`` which causes issues if
         # we are iterating over ``data.readCBs`` at the same time. We therefore