Remove shared transport

I'm thinking of deprecating the shared transport [1] and remove it in 4.0. The replacement would be fork channels [2].

Here's my reasoning:

• Shared transports are quite a complex beast: initialization (ref counting), cluster-name and local-addr are not used in TP when shared, duplicate logic. Removing this will make the code base smaller
• All protocols above shared transports are not shared, e.g. FD_SOCK, NAKACK, UNICAST etc all maintain their own threads, retransmission tables, sockets etc. With fork channels, everything up to the FORK protocol is shared
• TUNNEL doesn't work with shared transports (throws an exception)
• Hidden insertion of TP$ProtocolAdapter into the stack when shared transports are used
• Unneeded cost of sending N-1 messages (e.g. with TCP). Currently we send a message with dest null and no IP multicast capable transport to all physical addresses in the transport, which is a waste

Thoughts ? My +100 for removing shared transports in 4.0...

[1] http://www.jgroups.org/manual/html/user-advanced.html#SharedTransport
[2] http://www.jgroups.org/manual/html/user-advanced.html#ForkChannel