MFC all changes to install(1) through r246784. Notable functional

MFC all changes to install(1) through r246784.  Notable functional
changes are:

r245617:
Introduce six new options from NetBSD:
 * -M <metalog>   Log metadata in mtree format.
 * -D <destdir>   Log paths relative to <destdir>.
 * -h <hash>      Log digest of type <hash>.
 * -T <tags>      Specify which mtree tags to log.
 * -l <linkflag>  Create hard or symbolic links (allows logging).
 * -U             Install without root privileges (owner, group, mode,
                  and flags can be logged via -M

NOTE: In the interest of compatibility with NetBSD and because it is the
obvious letter, the nearly useless -M option (disable mmap) has been
repurposed.

Sponsored by:	DARPA, AFRL
Obtained from:	NetBSD
Reviewed by:	bz

r245312:
Implement the -N <dbdir> option which allows an alternate passwd and
group file to be used.  This is useful for installing on systems where
a user or group does not currently exist.

Sponsored by:	DARPA, AFRL
Obtained from:	NetBSD

git-svn-id: svn://svn.freebsd.org/base/stable/9@248331 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f