MFC r256687:

Upgrade to the latest version of mtree from NetBSD. This revision
re-removes the printing of size for non-regular files, supports
type-less root (.) entries as seen in a couple ports, and corrects a bug
in -N that caused expanded Subversion $FreeBSD$ strings in comments to
be processed as /etc/group entries.

Includes one trivial portability fix (including <stdint.h> in three
files) that has been committed upstream.

Approved by: re (glebius)