Close the connection if a stream management client fails to respond to
an acknowledgement request within 60 seconds. This number of seconds
can be changed with the new "ack_timeout" option, and the mechanism can
be disabled by specifying 'infinity'.
As a side effect of this change, a new acknowledgement is no longer
requested before the response to the previous request is received.
Old style websocket do use binaries for transferring data to C2S, so when
we buffer that data we need to handle it different than list of #xml structs
used by new style connections.
This fixes github issue #515.