- 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 r260017:

Mark unused static inline functions defined by the PCTRIE_DEFINE() macro
as __unused, so warnings about them are avoided.

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

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

- pctrie really only requires two byte alignment so that there is a single
bit available for a flag in the pointer. However, it felt more correct
to enforce natural alignment of the key pointer. Unfortunately on
32bit architectures 64bit integers are not always naturally aligned.
Change the assert to enforce only 32bit alignment of the 64bit key for
now to fix the build. A more correct fix would be to properly sort
the struct buf fields which definitely suffer from bloat due to padding.

- Add a new general purpose path-compressed radix trie which can be used
with any structure containing a uint64_t index. The tree code
auto-generates type safe wrappers.
- Eliminate the buf splay and replace it with pctrie. This is not only
significantly faster with large files but also allows for the possibility
of shared locking.

Reviewed by: alc, attilio
Sponsored by: EMC / Isilon Storage Division