MFC r298551, r298679, r298680:
fsck_ffs: use uint32_t for closedisk().

fs_ncg is of type uint32_t, and we were indexing it with an int.
Fixed this using an unsigned type.

Reviewed by: mckusick

MFC r260068, r260069, r260076

Add the -R option to allow fsck_ffs to restart itself when too many critical
errors have been detected in a particular run.

Clean up the global state variables so that a restart can happen correctly.

Separate the global variables in fsck_ffs and fsdb to their own file. This
fixes header sharing with fscd.

Correctly initialize, static-ize, and remove global variables as needed in
dir.c. This fixes a problem with lost+found directories that was causing
a segfault.

Correctly initialize, static-ize, and remove global variables as needed in
suj.c.

Initialize the suj globals before allocating the disk object, not after.
Also ensure that 'preen' mode doesn't conflict with 'restart' mode

Obtained from: Netflix

MFC r260068, r260069, r260076

Add the -R option to allow fsck_ffs to restart itself when too many critical
errors have been detected in a particular run.

Clean up the global state variables so that a restart can happen correctly.

Separate the global variables in fsck_ffs and fsdb to their own file. This
fixes header sharing with fscd.

Correctly initialize, static-ize, and remove global variables as needed in
dir.c. This fixes a problem with lost+found directories that was causing
a segfault.

Correctly initialize, static-ize, and remove global variables as needed in
suj.c.

Initialize the suj globals before allocating the disk object, not after.
Also ensure that 'preen' mode doesn't conflict with 'restart' mode

Obtained from: Netflix