1.0.43.30: threads: Initial implementation of ATOMIC-INCF for arrays.

1.0.43.30: threads: Initial implementation of ATOMIC-INCF for arrays.

  * Teach SB-IMPL::EXPAND-ATOMIC-FROB to deal with unboxed
vectors of words as places.

  * Define SB-KERNEL:%ARRAY-ATOMIC-INCF/WORD by analogy to
SB-KERNEL:%RAW-INSTACE-ATOMIC-INCF/WORD.

  * Add SB-KERNEL:%ARRAY-ATOMIC-INCF/WORD to the VM fndb.

  * While we're here, define an interpreter stub for
%ARRAY-ATOMIC-INCF/WORD.  %RAW-INSTANCE-ATOMIC-INCF/WORD
still needs one, but that's out of scope right now.

  * Note that this is just the arch-independent parts of
ATOMIC-INCF for arrays, the per-arch parts will be separate
commits.