Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

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

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

s,KOBJMETHOD_END,DEVMETHOD_END,g in order to fully hide the explicit mention
of kobj(9) from device drivers.

Add ssm(4), which serves as a glue device allowing devices beneath the
scalable shared memory node, which is used in large UltraSPARC III based
machines to group snooping-coherency domains together, like schizo(4) to
be treated like nexus(4) children.