0.8.21.5:

0.8.21.5:
	Enable faster REPLACE on declared specialized arrays.

	Overview of necessary machinery:
	* New %VECTOR-RAW-BITS and %SET-VECTOR-RAW-BITS functions/VOPs
	  which automatically take into account VECTOR-DATA-OFFSET
	  (eliminates tedium associated with previous bit-bashing code
	   and makes things slightly faster).  It's not clear if the
	  old %RAW-BITS and %SET-RAW-BITS functions need to remain;
	* Generalize the old bit-bashing code to generate bit-bashers
	  for differently sized "bytes" (1-bit, 2-bit, 4-bit, etc.);
	* Add REPLACE transforms for most specialized array types
	  (those with elements not larger than the word size);
	* Replace various incantations of COPY-FROM-SYSTEM-AREA,
	  COPY-TO-SYSTEM-AREA, BIT-BASH-COPY, etc. with their new
	  width-aware equivalents (this accounts for the bulk of the
	  changed files, if not the changed lines);
	* Add systematic tests for UB*-BASH-{FILL,COPY};
	* Add generalized SUBSEQ and COPY-SEQ transforms while we're
	  at it (FILL would be nice to have, but is a little bit
	  trickier to do in the general case).

	These changes also open up the possibility of removing %BYTE-BLT
	  from the sources.  Benefits: decrease in the number of
	  WITHOUT-GCING forms required, less calling out to C, more of
	  the system in Lisp, etc.  %BYTE-BLT remains in this version,
	  but may be removed if there is sufficient support for its
	  removal.