- 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

Bring over the initial, CPU-only UART support for the AR933x SoC.

This implements the kernel glue needed (getc, putc, rxready).

This isn't a 16550 UART, even if the datasheet overview claims so.

The Linux ar933x support was used as a reference, however the uart code
is a reimplementation.

Attentive viewers will note that the uart code is based off of the ns8250
code and the UART bus code is a stubbed-out version of this. I'll be
replacing it with non-stubbed versions soon, making this a fully featured
driver.

Tested:

* AP121 reference board (AR933x), booting through the mountroot> prompt;
then doing some basic interactive tests in ddb.