1.0.5.6: compare-and-swap / instance-set-conditional refactoring

1.0.5.6: compare-and-swap / instance-set-conditional refactoring

 * Rename *-COMPARE-AND-EXCHANGE *-COMPARE-AND-SWAP.

 * DEFINE-FULL-COMPARE-AND-SWAP, use it to implement
   %INSTANCE-COMPARE-AND-SWAP (previously %INTANCE-SET-CONDITIONAL) on x86oids.

 * Implement %SIMPLE-VECTOR-COMPARE-AND-SWAP. Not used right now, but required
   by a forthcoming patch.

 * Implement non-x86oid (non-threaded) versions of the above.

 * Check that the slot isn't raw in DEFINE-STRUCURE-SLOT-COMPARE-AND-SWAP.

 * Whitespace.