- 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

Organize some members of ucontext_t in the same order they are in the
trap frame. These are usually not used, and so this changes very little.

MFC after: 5 days

MFppc64:

Kernel sources for 64-bit PowerPC, along with build-system changes to keep
32-bit kernels compiling (build system changes for 64-bit kernels are
coming later). Existing 32-bit PowerPC kernel configurations must be
updated after this change to specify their architecture.

/* -> /*- for license, minor formatting changes

Use the version field to identify the partial context used by
KSE process-scope threads.

Kernel changes for libthr (and probably libpthread).

include/ucontext.h
- remove trapframe and switch over to 'generic' description of machine
state. Include version field to help with future modifications.
Include floating point and altivec state, and hopefully align
correctly

powerpc/copyinout.c
- fill out casuptr() sync primitive, required by kern_umtx.c

powerpc/machdep.c
- shifted proc0/thread0/pcpu setup to before cninit, since
syscons -> make_dev -> devlock requires a valid curthread
- implemented get_mcontext/set_mcontext
- recast sendsig/sigreturn to use get/set_mcontext and new
ucontext struct. floating point now saved
- TODO: save/restore altivec state

powerpc/vm_machdep.c
- implemented cpu_thread_setup/cpu_set_upcall/cpu_set_upcall_kse
- eliminated trailing whitespace

Submitted by: Suleiman Souhlal <refugee@segfaulted.com>, ucontext by grehan

Minor style tweaks.

Beginnings of the powerpc machine dependant includes.

Reviewed by: obrien
Obtained from: NetBSD