MFC r248294, r248296:

r248294 (pjd):

Delete requests can be larger than MAXPHYS.

r248296 (pjd):

Minor corrections.
MFC r248286 (pjd):

Removed redundant includes.
MFC r252380:
Unbreak "zfs jail" and "zfs unjail" (broken in stable/9 since r249643)

I missed to register zfs_ioc_jail and zfs_ioc_unjail as legacy ioctl's
with the new zfs_ioctl_register_legacy() function.

These operations do not modify pools or datasets so there is no need to
log them to pool history.

Reported by:	Alexander Leidinger <netchild@FreeBSD.org> on current@