Pull up the following revisions, all via patch, requested by msaitoh
in ticket #1669:

sys/arch/x86/include/specialreg.h              1.204-1.206, 1.208

- Add Intel CPUID 0x07 %ecx bit 24 BUS_LOCK_DETECT.
- Add AMD CPUID 0x80000008 %ebx bit 30 IBPB_RET and CPUID 0x8000000a
  %edx bit 29 BusLockThreshold.
- Fix typo in comment.

(martin)