- Copy stable/10 (r259064) to releng/10.0 as part of the
10.0-RELEASE cycle.
- Update __FreeBSD_version [1]
- Set branch name to -RC1

[1] 10.0-CURRENT __FreeBSD_version value ended at '55', so
start releng/10.0 at '100' so the branch is started with
a value ending in zero.

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

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

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

Merge from tbemd:

Convert from using MACHINE_ARCH to MACHINE_CPUARCH. Hoist path statement
up into the top Makefile rather than repeating it on every arch Makefile.

Repo copy libpthreads to libkse.
This introduces the WITHOUT_LIBKSE nob,
and changes WITHOUT_LIBPTHREADS to mean with neither threading libs.
Approved by: re(kensmith)

Rethink the MD interfaces for libpthread to account for
archs that can (or are required to) have per-thread registers.

Tested on i386, amd64; marcel is testing on ia64 and will
have some follow-up commits.

Reviewed by: davidxu

Take the same approach for i386 as that for ia64 and amd64. Use
the userland version of [gs]etcontext to switch between a thread
and the UTS scheduler (and back again). This also fixes a bug
in i386 _thr_setcontext() which wasn't properly restoring the
context.

Reviewed by: davidxu

Move the machine specific files from sys/Makefile.inc and put them
in a machine specific makefile. While here, sort the sub-directories
in Makefile and remove _atomic_lock.S from all makefiles.