- 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

I completely fubared this. An empty EXPORT_SYMS= is not valid. I know I
build this several times, and even tested loaded the module. I must have
changed something right before commit.

Pointed out by: bde

opt_kstack_pages.h is not needed anymore. It would have been a Bad Thing
if it had been different to the running kernel.

Add an a.out exec module.