Replacement stalled block logic. Depending on the situation, it will either disconnect
the peer (as previous behaviour), or it will reselect a syncnode (e.g. when 500 blocks
have been received from the syncnode).
Allow nodes to send version messages more than once.
Report ping times at they arrive.
Antisocial (needs CaughtUp)
indentation
Rename MarkBlockAsReceived to MarkBlockAsRequested to reduce confusion.
Force selection of a new syncnode since the current syncnode is about to stop sending blocks.
Display unknown commands received.