multicast support

[Vance Shipley]

The (undocumented) gen_udp options gen_udp add_membership and drop_membership 
do not work simply because they were left out of the list of allowable options.
The following patch against R9B-1 is tested and working:


$ diff inet.erl inet.erl.dist
373,374c373
<      broadcast, dontroute, multicast_if, multicast_ttl, multicast_loop,
<      add_membership, drop_membership].
---
>      broadcast, dontroute, multicast_if, multicast_ttl, multicast_loop].


This, along with another bug, were previously reported by Carlos <carlos@REDACTED>:


   http://www.erlang.org/ml-archive/erlang-questions/200112/msg00068.html


      -Vance


Vance Shipley
Motivity Telecom Inc.
+1 519 240 3684
vances@REDACTED