Update to r42118:
Remove the vinum chapter. It has been surpassed by other solutions from
GEOM and ZFS. The existing version is archived in
http://docs.freebsd.org/doc/ . Illustration images in
doc/share/images/books/handbook/vinum/ remain, as they are used by
non-English translations. -doc mailing list discussion thread:
http://lists.freebsd.org/pipermail/freebsd-doc/2013-June/022216.html

Approved by: bcr (mentor)