MFC r260068, r260069, r260076

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

git-svn-id: svn://svn.freebsd.org/base/stable/10@260178 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f