MFC r249930:
Added a sysctl to control the maximum size of a delete request
MFC:	r251186

Fix a long standing logic bug introduced in r167814.  The code was added to
get RSDP from loader(8) hint via kenv(2) but the bug nullified the new code
and we always fell back to the previous method, i. e., sysctlbyname(3).
MFC r249931:
Added Dataset Management defines to be used by TRIM
MFC r249933:
Added the ability to send ATA identify and TRIM commands via SCSI
MFC 248167:
Fix the 'C' field for a running thread to match the behavior described
in the manpage by having it display the current CPU (ki_oncpu) rather
than the previously used CPU (ki_lastcpu).  ki_lastcpu is still used for
all other thread states.