- Remapped ldi_handle_t to struct block_device * which is much more useful

- Remapped ldi_handle_t to struct block_device * which is much more useful
- Added liunx block device headers to sunldi.h
- Made __taskq_dispatch safe for interrupt context where it turns out we
  need to be useing it.
- Fixed NULL const/dest bug for kmem slab caches
- Places debug __dprintf debugging messages under a spin_lock_irqsave
  so it's safe to use then in interrupt handlers.  For debugging only!

git-svn-id: https://outreach.scidac.gov/svn/spl/trunk@64 7e1ea52c-4ff2-0310-8f11-9dd32ca42a1c