[conformal/btcd] 886281: Use separate max protocol version.

[Dave Collins]

  Branch: refs/heads/master
  Home:   https://github.com/conformal/btcd
  Commit: 886281993a3b1e7a1452037762a42adee33b7bb1
      
https://github.com/conformal/btcd/commit/886281993a3b1e7a1452037762a42adee33b7bb1
  Author: Dave Collins <da...@conformal.com>
  Date:   2014-03-28 (Fri, 28 Mar 2014)

  Changed paths:
    M peer.go

  Log Message:
  -----------
  Use separate max protocol version.

This commit modifies peers to use a max protocol version that is specified
as a constant in the peer code as opposed to the btcwire.ProtocolVersion
constant.

This allows btcwire to be updated to support new protocol versions without
causing peers to claim they support a protocol version which they actually
don't.