MCAS changes from Matt

MCAS changes from Matt

Change static max allocators to 30.  Add atomic add/sub macros returning
original value, based on CASIO.  Add interfaces to add and remove generic
allocator caches.  Add atomic inc/dec/sub macros using MCAS primitives.
Add inline assembly for x86_64 and shim for Solaris (9+) atomic operations,
providing Solaris x86 and alternate shim for Solaris Sparc.  Set interface
adapted for iteration and generalized for use with opaque key, value
pointers.  File cas_skip_func.c provides kv interface, cas_skip_adt.c
provides kv interface, plus iteration on skip lists.  Casual dependencies
on stdio and exit() defined out.

LICENSE BSD

Reviewed-on: http://gerrit.openafs.org/214
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>