Improved the performance of kernel profiling on MULTIPROCESSOR, and possible to get profiling data for each CPU.

In the current implementation, locks are acquired at the entrance of the mcount
internal function, so the higher the number of cores, the more lock conflict
occurs, making profiling performance in a MULTIPROCESSOR environment unusable
and slow. Profiling buffers has been changed to be reserved for each CPU,
improving profiling performance in MP by several to several dozen times.

- Eliminated cpu_simple_lock in mcount internal function, using per-CPU buffers.
- Add ci_gmon member to struct cpu_info of each MP arch.
- Add kern.profiling.percpu node in sysctl tree.
- Add new -c <cpuid> option to kgmon(8) to specify the cpuid, like openbsd.
For compatibility, if the -c option is not specified, the entire system can be
operated as before, and the -p option will get the total profiling data for
all CPUs.

Fix false sharing problems with cpu_info. Identified with tprof(8).
This was a very nice win in my tests on a 48 CPU box.

- Reorganise cpu_data slightly according to usage.
- Put cpu_onproc into struct cpu_info alongside ci_curlwp (now is ci_onproc).
- On x86, put some items in their own cache lines according to usage, like
the IPI bitmask and ci_want_resched.

mi_userret(): take care of calling preempt(), set spc_curpriority directly,
and remove MD code that does the same.

branches: 1.2.2;
s/static inline/static __inline/g for consistency.

branches: 1.1.18; 1.1.20;
New files for OR1K support