[Mldonkey-users] Avoid adding a MLDonkey client twice

[spiralvoice]

Hi,

I found these clients in pending upload slots and added them as friend 
to find out more about them:

        (* The list of known friends *)
 friends = [
  {     client_network = Donkey
     client_addr = ("1.2.3.4", 17970)
     client_md4 = "ABABABABABABABABBAA"
     client_name = mldonkey
     client_age = 82162612
     client_last_filereqs = 0
     client_overnet = true
};
  {     client_network = Donkey
     client_addr = ("1.2.3.4", 4662)
     client_md4 = CDCDCDCDCDCDCDCDCDCDCDCD
     client_name = mldonkey
     client_age = 82162829
     client_last_filereqs = 0
     client_overnet = false
};]

As you can see it seems to be the same client, one MLDonkey daemon 
using Donkey and Overnet network. According to pending pending slots 
the client on port 4662 has client number 61251 (tML, 532.0k upload) 
and the client on port 17970 has client number 57416 (OVR, 1.3M 
upload).

We should build some identification mechanism to avoid adding the same 
MLDonkey client twice in our client list:

if c.client_type = Brand.mldonkey3 then begin
        if test_client_has_overnet_enabled then begin
                add_flag c.client block_overnet
        end
end

so we can recognize if this MLDonkey tries to connect us on Overnet and 
we can refuse it then, but not black_list. We should instead send a 
message to this client so it knows why we don´t let it connect to us.

- spiralvoice