- 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)

MFC r275779, r275963, r276101, r276161, r276297:

Move ofw_cpu.c to sys/dev/ofw so that it can be used by other
architectures.

Add driver for CPU frequency/voltage control on the Raspberry Pi.

On initialization, do not use bcm_mbox_intr() to read the pending messages.
This fixes the hang that happens on boot while initializing the cpufreq on
Raspberry Pi.

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

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

Convert bcm2835_mbox to the new mbox interface.

Reviewed by: gonzo

Add barebone Raspberry Pi port. Supported parts:
- Interrupts controller
- Watchdog
- System timer
- Framebuffer (hardcoded resolution/bpp)