Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Sweep man pages replacing ad -> ada.

Approved by: re (blackend)
MFC after: 1 week
X-MFC note: stable/9 only

mdoc: order prologue macros consistently by Dd/Dt/Os

Although groff_mdoc(7) gives another impression, this is the ordering
most widely used and also required by mdocml/mandoc.

Reviewed by: ru
Approved by: philip, ed (mentors)

Add a geom class to map Linux LVM logical volumes.

The logical disks will appear as /dev/lvm/<vol group>-<logical vol>, for
instance /dev/lvm/vg0-home. G_LINUX_LVM currently supports linear stripes with
segments on multiple physical disks. The metadata is read only, logical
volumes can not be allocated or resized.

Reviewed by: Ivan Voras

Previously known as geom_lvm(4), rename requested by des, phk.