- Copy stable/10@296371 to releng/10.3 in preparation for 10.3-RC1
builds.
- Update newvers.sh to reflect RC1.
- Update __FreeBSD_version to reflect 10.3.
- Update default pkg(8) configuration to use the quarterly branch.

Approved by: re (implicit)

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

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

Expose stripe offset and stripe size through libgeom and geom(8) userland
utilities.

Reviewed by: pjd, mav (earlier version)

- Add a new ioctl for getting the provider name of a geom provider.
- Add a routine for looking up a device and checking if it is a valid geom
provider given a partial or full path to its device node.

Reviewed by: phk
Approved by: pjd (mentor)

Use 'dowrite' as an argument name instead of too general 'write'.

Implement and document some utility functions that can be used to communicate
with GEOM providers.

OK'ed by: phk