todo

fax相关的东西

B constrain job parameters for non privileged users
B shut cmd uses local time
B what to do with disable modem reason msg
B commands for registering inbound document distribution/routing
  (chown is there for assignment; maybe need notification mechanisms)
B fix passwd file locking for concurrent updates
H return tail -f log/... for status
H inverse shut command
H restrict active page count and/or number of jobs per-user
H start/stop queuer
H trigger status format strings
H adduser must be able to set uid as well
H per-user controls
H format conversion during document retrival (e.g. TIFF->PS)
? limits on the recvq cache?
? take msgs from control channel ala SMTP (e.g. SHUT, DISABLE)
? should ADMIN work like USER (i.e. take account name instead of passwd)