- Copy stable/10@285827 to releng/10.2 in preparation for 10.2-RC1
builds.
- Update newvers.sh to reflect RC1.
- Update __FreeBSD_version to reflect 10.2.
- Update default pkg(8) configuration to use the quarterly branch.[1]

Discussed with: re, portmgr [1]
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

Begin separating out the TX DMA setup in preparation for TX EDMA support.

* Introduce TX DMA setup/teardown methods, mirroring what's done in
the RX path.

Although the TX DMA descriptor is setup via ath_desc_alloc() /
ath_desc_free(), there TX status descriptor ring will be allocated
in this path.

* Remove some of the TX EDMA capability probing from the RX path and
push it into the new TX EDMA path.