mips: Convert lock.h to membar_release/acquire.

mips: Brush up __cpu_simple_lock.

- Eradicate last vestiges of mb_* barriers.

- In __cpu_simple_lock_init, omit needless barrier. It is the
caller's responsibility to ensure __cpu_simple_lock_init happens
before other operations on it anyway, so there was never any need
for a barrier here.

- In __cpu_simple_lock_try, leave comments about memory ordering
guarantees of the kernel's _atomic_cas_uint, which are inexplicably
different from the non-underscored atomic_cas_uint.

- In __cpu_simple_unlock, use membar_exit instead of mb_memory, and do
it unconditionally.

This ensures that in __cpu_simple_lock/.../__cpu_simple_unlock, all
memory operations in the ellipsis happen before the store that
releases the lock.

- On Octeon, the barrier was omitted altogether, which is a bug --
it needs to be there or else there is no happens-before relation
and whoever takes the lock next might see stale values stored or
even stomp over the unlocking CPU's delayed loads.

- On non-Octeon, the mb_memory was sync. Using membar_exit
preserves this.

XXX On Octeon, membar_exit only issues syncw -- this seems wrong,
only store-before-store and not load/store-before-store, unless the
CNMIPS architecture guarantees it is sufficient here like
SPARCv8/v9 PSO (`Partial Store Order').

- Leave an essay with citations about why we have an apparently
pointless syncw _after_ releasing a lock, to work around a design
bug^W^Wquirk in cnmips which sometimes buffers stores for hundreds
of thousands of cycles for fun unless you issue syncw.

Indent branch delay slots in asm code (from skrll@).
Be consistent within this file with how asm code is formatted.

more const.

Rework cavium support in preparation for MULTIPROCESSOR support

branches: 1.18.14; 1.18.32;
Major merge forward from matt-nb5-mips64.
New fixup code.
New common SPL code.
New common interrupt code.
Move related variables into structures.
Cleanup locore (move MD variable into it).
Kill StudlyCaps
Use PCU for FPU

branches: 1.17.6; 1.17.8; 1.17.10;
Use userspace version unless _HARDKERNEL. Otherwise we use atomic
cas to implement spinlocks and spinlocks to implement atomic cas....
which might suck.

Since the userspace version uses ll/sc, which doesn't exist on
R2000/R3000, rump will not work on those platforms. *snif* (well,
pthread in general AFAICT).

branches: 1.16.8; 1.16.16;
Remove clause 3 and 4 from TNF licenses

branches: 1.15.14; 1.15.16; 1.15.18;
- Change _lock_cas and friends to do "compare and swap" instead of "compare
and set".
- Rename them to _atomic_cas_uint, _atomic_cas_ulong etc and provide strong
aliases for the other names CAS goes by.

branches: 1.14.2;
Merge the ppcoea-renovation branch to HEAD.

This branch was a major cleanup and rototill of many of the various OEA
cpu based PPC ports that focused on sharing as much code as possible
between the various ports to eliminate near-identical copies of files in
every tree. Additionally there is a new PIC system that unifies the
interface to interrupt code for all different OEA ppc arches. The work
for this branch was done by a variety of people, too long to list here.

TODO:
bebox still needs work to complete the transition to -renovation.
ofppc still needs a bunch of work, which I will be looking at.
ev64260 still needs to be renovated
amigappc was not attempted.

NOTES:
pmppc was removed as an arch, and moved to a evbppc target.

Merge nick-csl-alignment.

branches: 1.12.6; 1.12.14; 1.12.18; 1.12.22; 1.12.24;
Pacify lint/gcc.

s/___asm/__asm/

Merge newlock2 to head.

branches: 1.9.6;
Adjust asm constraints for more pickier gcc4.

branches: 1.8.4; 1.8.6; 1.8.8; 1.8.14;
inline -> __inline

Remove leading __ from __(const|inline|signed|volatile) -- it is obsolete.

merge ktrace-lwp.

branches: 1.5.16;
Move __cpu_simple_lock_t and __SIMPLELOCK_{UN,}LOCKED to machine/types.h
so that they can be used in a namespace-friendly way.

branches: 1.4.6;
Drop the _KERNEL test; these functions are needed for SMP and other ports
don't bother with a _KERNEL check.

Bring down from nathanw_sa branch.

branches: 1.2.6; 1.2.10; 1.2.14;
Let each platform typedef the new __cpu_simple_lock_t, which should
be the most efficient type used for the atomic operations in the
simplelock structure, and should also be __volatile.

Require that each each MACHINE/MACHINE_ARCH supply a lock.h. This file
contains the values __SIMPLELOCK_LOCKED and __SIMPLELOCK_UNLOCKED, which
replace the old SIMPLELOCK_LOCKED and SIMPLELOCK_UNLOCKED. These files
are also required to supply inline functions __cpu_simple_lock(),
__cpu_simple_lock_try(), and __cpu_simple_unlock() if locking is to be
supported on that platform (i.e. if MULTIPROCESSOR is defined in the
_KERNEL case). Change these functions to take an int * (&alp->lock_data)
rather than the struct simplelock * itself.

These changes make it possible for userland to use the locking primitives
by including <machine/lock.h>.