- PONG is no longer a response (its type value is lower than 0x8000), because it's actually just a "still alive" notification, which happens on demand.
- PING & PONG don't reach the handler level any more, but are directly handled at connection level. There is no point in making them flexible, as a PING really just test that connection is established.
This fixes client's unability to send ping, because of MTClientConnection.ask prototype being incompatible with ClientConnection.ask.


git-svn-id: https://svn.erp5.org/repos/neo/branches/prototype3@899 71dcc9de-d417-0410-9af5-da40c76e7ee4