MFC change 196383:

MFC change 196383:
 Remove the dependency on the kernel -- in particular the gctl request to
 the GEOM_BSD class -- to translate the absolute offsets in the label to
 relative ones. This makes bslabel(8) work correctly with GEOM_PART and
 also when the BSD label is nested under arbitrary partitioning schemes.

Inspired by:	Eygene Ryabinkin <rea-fbsd@codelabs.ru>
Approved by:	re (kib)

git-svn-id: svn://svn.freebsd.org/base/stable/8@196384 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f