Re: (ITS#4666) -d ? says: unrecognized log level '?'

[mcs@pearlcrescent.com]

I do not have time to learn about pcache right now, but I did some quick 
testing on your latest changes without it and everything seems to be OK. 
  I would suggest that instead of reporting unrecognized log levels like 
this:

   unrecognized log level "foo" (deferred)

It might be better to report this during initial startup:

   unrecognized log level "foo" (ignored for now)

And when you are sure it is truly an error, report:

   unrecognized log level "foo" (exiting)

I would also replace this message:

   NOTE: custom log subsystems may be later installed by specific code

with something like:

   NOTE: Logging subsystems defined by overlays are not listed.

-Mark