struct disklabel.
Functionality lost:
1. struct disklabel used to be updated to contain bsize, fsize, cpg.
This information was used to locate the alternative superblock in
the filesystem if the primary superblock was corrupted. We need
to find a new place to store this information if we need this
functionality.
2. On vax SMD drives that contained bad sector lists, the newfs program
knew how to get the offset and skip to the correct location in order
to place the label.
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