MFC r275533:

Sync with Illumos.  This have no effect to FreeBSD.

Illumos issue:
    5100 sparc build failed after 5004

MFC after:	2 weeks
MFV r275534:

Sync with Illumos.  This have no effect to FreeBSD.

Illumos issue:
    5285 pass in cpu_pause_func via pause_cpus

MFC after:	2 weeks
MFV r275535:

Unexpand ISP2() and MSEC2NSEC().

Illumos issue:
    5255 uts shouldn't open-code ISP2

MFC after:	2 weeks
MFV r275536:

Illumos issue:
    3363 Mark non-returning functions in ctftools

MFC after:	2 weeks