hier.7: various improvements
Reviewed by: imp
Pull Request: https://github.com/freebsd/freebsd-src/pull/831
(cherry picked from commit 03ee09148950c9ea99987bfee8a769473079745b)
(cherry picked from commit 94dedfdfa96baef02e4ad661512a267ae5647d7b)
(cherry picked from commit a5b07274fcaf71fc9c14947a75fbe0a13d381a79)
(cherry picked from commit f19875b66bf403ed5c57f82bbe2a3f42475d0a06)