- 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

Allow pty(4) to be loaded as a kld.

Unfortunately, the wrappers that are present in pts(4) don't have the
mechanics to allow pty(4) to be unloaded safely, so I'm forcing this kld
to return EBUSY. This also means we have to enable some extra code in
pts(4) unconditionally.

Proposed by: rwatson