0: No output. Default for mount_mfs unless -N specified
1: Output size of partition and cylinder groups.
2: Follow with a progress-bar line of dots (scaled to finish at RH margin)
3: Include a single line of alternate suberblock addresses before progress
bar. Default for newfs.
4: Output lots of lines of alternate superblock numbers that scroll madly
up the screen.
If -N given, newfs/mount_mfs exits before displaying any progress bar.
Output constrained (almost always) to 1 column less than the terminal width.
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