Also, be a bit more conservative with the clean flag: don't mark the FS
clean when we know there may still be errors (user anserwed 'n' to
a question, or fsck says "you must rerun fsck").
- added missing prototypes, and made local functions static
- removed parallel preening code; this is part of fsck(8)
- use printing utilities from fsck(8)
- Makefile does not make links to fsck and fsck.8
- removed -l maxparallel option. It has no meaning anymore.