- 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

Rework how drm maps are handled.

* On 32 bit platforms we steal the upper 4 bits of the map handle
to store a unique map id.
* On 64 bit platforms we steal the upper 24 bits.

Resolves issues where the offsets that are handed to mmap may overlap the VRAM on some cards.

Tested on: radeon, intel, mga, and via.

This will break nouveau. I will spin new patches shortly.

Welcome drm support for VIA unichrome chips.

MFC after: 2 weeks