[RFC] removing comm half-closed mechanism

[Amos Jeffries]

While working on redesign of the ConnStateData functionality I have come 
to suspect that the half-closed FD monitoring feature is possibly 
defunct now.

In particular ConnStateData now provides stopReceiving()/stopSending() 
members to explicitly finish closing the connection at an appropriate 
time in the traffic and a set of accessors to monitor the half-closed 
nature of connections in a much more deterministic directional way. It 
would seem the FD monitoring handler which is set for half-closed might 
still be useful, but this can be moved to a ConnStateData handler instead.

Anyone have a reason why we should keep all the half-closed code in 
comm.cc ?

Amos