Syntax :  .backup
	  .backup -b
	  .backup -t [<number of days>]

Results:  By itself, toggles (on/off) the archiving status of system logs.
	  When on, system logs are archived at midnight to a timestamped
	  subdirectory in the main log directory.
	  With the -b option, performs an archive of logs immediately.
	  With the -t option, performs log trimming. This is deleting
	  of archived logs older than x days.
	  If <number_of_days> is specified, logs older than this many of
	  days will be deleted. If not specified, the system variable
	  TRIM_BACKUPS will be used, given it's larger than 0.

  NOTES:  When logs are archived, this then clears the logs in the main
	  log directory.

See also: .readlog