[mythtv] Timestamps on backend log

[Preston Crow]

I've noticed that the backend log doesn't have timestamps, but the
frontend log does.  Would it be a big deal to add them?

It looks like it would require some work on the function av_log() with a
scan through the string for newlines (at least one place uses multiple
calls with only the last one having a newline).  The other option would
be to require all log messages to be passed as a unit, cleaning up any
place that sends partial lines.  I'm in favor of the second option.

I could give it a go if there's agreement that it's a good idea and
someone more familiar with the code doesn't want to do it.

--PC