- 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

amdsbwd: new driver for AMD SB600/SB7xx watchdog timer

The hardware is compliant with WDRT specification, so I originally
considered including generic WDRT watchdog support, but decided
against it, because I couldn't find anyone to the code for me.
WDRT seems to be not very popular.
Besides, generic WDRT porbably requires a slightly different driver
approach.

Reviewed by: des, gavin, rpaulo
MFC after: 3 weeks