Victory! I've reworked caches with large objects which are

Victory!  I've reworked caches with large objects which are
based by vmalloc()'ed memory.  I now alloc a slab which is
roughly 32*spl_obj_size and in this block of memory I place
the slab descriptor, slab object descriptors, and objects
themselves.  This greatly reduces vmalloc lock contention.

Still some minor cleanup remains and fine tuning but
it's working pretty well.

git-svn-id: https://outreach.scidac.gov/svn/spl/trunk@139 7e1ea52c-4ff2-0310-8f11-9dd32ca42a1c