Change handling of `clean' file systems:

fsck_ffs-always_skipclean.diff - change fsck_ffs(8) to skip `clean' file
  systems by default
or
fsck_ffs-forceskipclean.diff - add new flag to fsck_ffs(8) to skip `clean' file
  systems
fsck_msdosfs-forceskipclean.diff - equivalent for fsck_msdosfs(8)
fsck-forceskipclean_passthru.diff - change fsck(8) to pass -C flag to fsck_*

fsck-parallel_changes.diff - applies to fsck(8):
- separate parallelization from preen mode
- add a new -P flag to use parallelization in non-preen mode
- add a new -Q flag to bypass one process per disk restriction

rc.d-y.diff - change rc.d/fsck script to not run preen mode at all when
  fsck_y_enable is set