- 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)

MFH (r276605, r282089): upgrade to latest Unbound
MFH (r276699, r276702, r277057): local control socket
MFH (r276599, r276612, r282087, r282088): build fixes

This brings in Unbound 1.5.3 from head. Local control sockets are now
supported and will be used by default for new installations. Existing
systems will continue to use TCP control sockets until the automated
setup script is re-run ("service local_unbound setup") and the service
restarted ("service local_unbound restart").

Approved by: re (kib)
Relnotes: yes

Upgrade to Unbound 1.5.1. Almost all our local changes to date have been
adopted upstream, greatly reducing the diff.

import unbound 1.5.0