Add timestamps to log messages (MSG_LOG)

[adrianghc]

Currently, log messages are timestamped and logged by the Launcher Module in the order that they arrive, which does not necessarily reflect the order in which they are sent. To fix this, messages should be timestamped by the modules that send them. In addition, by buffering a fixed number of messages before logging them (instead of logging messages as they arrive), the Launcher Module could sort all messages in the buffer by their timestamp before logging them, but this is an imperfect solution with many caveats. Alternatively, MSG_LOG messages could be sent synchronously instead of asynchronously.