Write status information to stdout instead of stderr.
Exit status when an error occurs musn't be 1, that is reserved for
indicating that messages are disabled.
These changes bring mesg(1) up to SUSv3 conformance.
Reviewed by: mike
This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.
Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.
