- 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 r270160:

Destroy the "qdiffsample_zone" UMA zone on unload to avoid a use-after-unload
panic easily triggered by running "sysctl -a" after unload.

Reported and tested by: Grenville Armitage <garmitage@swin.edu.au>
Approved by: re(gjb)

Merge r261590: Fixup for r261590 (vnet sysctl handlers cleanup)

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

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

Import an implementation of the CAIA Delay-Gradient (CDG) congestion control
algorithm, which is based on the 2011 v0.1 patch release and described in the
paper "Revisiting TCP Congestion Control using Delay Gradients" by David Hayes
and Grenville Armitage. It is implemented as a kernel module compatible with the
modular congestion control framework.

CDG is a hybrid congestion control algorithm which reacts to both packet loss
and inferred queuing delay. It attempts to operate as a delay-based algorithm
where possible, but utilises heuristics to detect loss-based TCP cross traffic
and will compete effectively as required. CDG is therefore incrementally
deployable and suitable for use on shared networks.

In collaboration with: David Hayes <david.hayes at ieee.org> and
Grenville Armitage <garmitage at swin edu au>
MFC after: 4 days
Sponsored by: Cisco University Research Program and FreeBSD Foundation