an _LKM.
This adds pools to the list of things that lkms must do manually
because they're set up with link sets. Not that there's anything
wrong with link sets, but that we need to try harder to remember that
lkms are second class citizens. Of a sort.
to pool_init. Untouched pools are ones that either in arch-specific
code, or aren't initialiased during initial system startup.
Convert struct session, ucred and lockf to pools.
atatat