Fix a time calculation error in ctlstat_standard().

ctlstat.c:	When converting a timeval to a floating point
		number in ctlstat_standard(), cast the nanoseconds
		calculation to a long double, so we don't lose
		precision.  Without the cast, we wind up with a
		time in whole seconds only.

Sponsored by:	Spectra Logic
MFC after:	3 days
Since UMA_ZONE_PCPU zones put a constraint on sizeof(struct pcpu), declared
as CTASSERT in MI pcpu.h, stop including all possible mutually exclusive
PCPU_MD_FIELDS fields into LINT kernels, due to brekaing
aforementioned CTASSERT.