If one of these fields is accidentally reassigned, it's possible for
threads to be oblivious to an existing lock. By making the fields
readonly, we will be notified at compile-time if we inadvertently
redefine one of these fields.
This enables modules to report messages to the message-sink, and thus to the commandline through the normal interface.
This simplifies handling multiple logging systems, and supports reporting logging from multiple concurrent controller instances.
This fixes#2225
This fixes#1575
Kenneth Skovhede