The CLI's set_logging logic seemed unnecessarily complicated to me.
This patch simplifies it, with an eye toward changing it to use RAII
objects in a subsequent patch.
I did not touch the corresponding MI code. That code seems incorrect
(nothing ever uses raw_stdlog, and nothing ever sets
saved_raw_stdlog). I didn't attempt to fix this, because I question
whether this is even useful for MI.
22f8b65e9b