fsck_s5 Phase 1B: rescan for More DUP

When a duplicate block is found in the filesystem, the filesystem is rescanned to find the inode that previously claimed that block. When the duplicate block is found, the following informational message is printed:

DUP I=I

Inode I contains block number B that is already claimed by the same or another inode or by a free list. This error condition generates the BAD/DUP error message in Phase 2. Inodes that have overlapping blocks can be determined by examining this error condition and the DUP error condition in Phase 1.