- 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 r279311:

In sys/arm/ti/am335x/am335x_rtc.c, fix a clang 3.6.0 warning about
am33x_rtc_softc::sc_irq_res (which is an array) never being NULL.

Submitted by: andrew

MFC r277042:

Add support to turn off Beaglebone with poweroff(8) or shutdown(8) -p.

To cut off the power we need to start the shutdown sequence by writing
the OFF bit on PMIC.

Once the PMIC is programmed the SoC needs to toggle the PMIC_PWR_ENABLE
pin when it is ready for the PMIC to cut off the power. This is done by
triggering the ALARM2 interrupt on SoC RTC.

The RTC driver only works in power management mode which means it won't
provide any kind of time keeping functionality. It only implements a way
to trigger the ALARM2 interrupt when requested.

Add support to turn off Beaglebone with poweroff(8) or shutdown(8) -p.

To cut off the power we need to start the shutdown sequence by writing
the OFF bit on PMIC.

Once the PMIC is programmed the SoC needs to toggle the PMIC_PWR_ENABLE
pin when it is ready for the PMIC to cut off the power. This is done by
triggering the ALARM2 interrupt on SoC RTC.

The RTC driver only works in power management mode which means it won't
provide any kind of time keeping functionality. It only implements a way
to trigger the ALARM2 interrupt when requested.

Differential Revision: https://reviews.freebsd.org/D1489
Reviewed by: rpaulo
MFC after: 2 weeks