when closing a  networking stream instead of input_FDClose().  It is due
to WIN32  because we have  to call  closesocket() instead of  close() to
close the socket. The problem was  : windows did not leave the multicast
group when closing the socket.

  * input_ext-plugins.c : where is located the function
  * *.h : function declaration
  * udp.c, http.c : these modules now call input_FDNetworkClose()