[conformal/btcd] d40cff: Expose a close ntfn channel to all RPC handlers.

[Dave Collins]

  Branch: refs/heads/master
  Home:   https://github.com/conformal/btcd
  Commit: d40cff64b0dc7904a5490cd04b029a78a7cd2bbf
      
https://github.com/conformal/btcd/commit/d40cff64b0dc7904a5490cd04b029a78a7cd2bbf
  Author: Dave Collins <da...@conformal.com>
  Date:   2014-06-27 (Fri, 27 Jun 2014)

  Changed paths:
    M rpcserver.go
    M rpcwebsocket.go

  Log Message:
  -----------
  Expose a close ntfn channel to all RPC handlers.

This commit modifies the RPC server such that all handlers now receive a
channel which will be notified when a client disconnects.  This
notification can then be used to stop long-running operations early when a
client disconnects.

This capability was already present for websocket clients, but this commit
exposes it to standard HTTP clients as well.