Merge r257996,r258001,r258069 from head: fixes for HyperV guest. - Set description string for VM_GUEST_HV (HyperV guest). - Add a brief comment about VM_GUEST and vm_guest_sysctl_names relationship. - CTASSERT that vm_guest range is covered by vm_guest_sysctl_names. Approved by: re (glebius)