MFC all change to makefs through r247052. Key functional changes

MFC all change to makefs through r247052.  Key functional changes
include:

r239562:
Add -p flag to create the image as a sparse file.

r242501:
If no contents keyword is specified, the default for files is
the named file.

r247041:
Add a -D flag that causes duplicate entries in an mtree manifest to be
treated as warnings rather than errors.

r247042:
Fix the -N option in manifest mode by using pwcache(3).  This also
speeds up image creation appreciably.

r247043:
Allow '.' components in manifest paths.  They are always the first
component of mtree -C and install -M output and are easily skipped.

r247052:
Support hardlinks in manifest files by the same logic as the treewalk
code.

git-svn-id: svn://svn.freebsd.org/base/stable/9@248293 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f