MFC r251732,251752:

MFC r251732,251752:

Add support for non-virtualised hhook points, which are uniquely identified by
type and id, as compared to virtualised hook points which are now uniquely
identified by type, id and a vid (which for vimage is the pointer to the vnet
that the hhook resides in).

All hhook_head structs for both virtualised and non-virtualised hook points
coexist in hhook_head_list, and a separate list is maintained for hhook points
within each vnet to simplify some vimage-related housekeeping.

Reviewed by:	scottl

git-svn-id: svn://svn.freebsd.org/base/stable/8@252535 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f