Inet bugs

[Carlos]

I found two small errors in the Erlang/OTP R8B.

1) With the current inet module there are not support to multicast (UDP)
sockets because the UDP socket options "add_membership" and
"drop_membership"
are not included in the implementation of the inet module.

Solution: Instead of the function inet:udp_options/0 which current
implementation is:

    udp_options() ->
	[reuseaddr, sndbuf, recbuf, header, active, buffer, mode, deliver,
	 broadcast, dontroute, multicast_if, multicast_ttl, multicast_loop].

use the following function

    udp_options() ->
	[reuseaddr, sndbuf, recbuf, header, active, buffer, mode, deliver,
	 broadcast, dontroute, multicast_if, multicast_ttl, multicast_loop,
	 add_membership,drop_membership].
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

This options should be documented.


2) The gen_udp:open(Port, Opts) function can receive a port number (integer)
or a service name (atom). When the Port argument is an atom, the service name is
translated to an integer (port number) using the getserv/1 function, but the
result of this function is not used in the last call of the gen_udp:open/2 function.

    The original code is the following:
    
    open(Port, Opts) ->
	Mod = mod(Opts),
	{ok,UP} = Mod:getserv(Port),
	Mod:open(Port, Opts).
    
    and the right code is,
    
    open(Port, Opts) ->
	Mod = mod(Opts),
	{ok,UP} = Mod:getserv(Port),
	Mod:open(UP, Opts).
		^^^^

-- Carlos