1.0.4.55: Optimized REPLACE and UB*-BASH-COPY routines

1.0.4.55: Optimized REPLACE and UB*-BASH-COPY routines

	* Expand simple cases of UB*-BASH-COPY inline to avoid full call
	  overhead and generate better code generally;
	* Handle more cases of REPLACE; we now optimize REPLACE on all
	  simple specialized array types (only element types <= n-word-bits
	  are handled generally, though);
	* Use a single COPY-SEQ and SUBSEQ transform rather than one per
	  specialized array type; generate inline copies for these too
	  when possible;
	* Tests;
	* Backend cleanup: introduce a FIND-SAETP to eliminate duplicate code;
	* Backend cleanup: change %{SET-,}VECTOR-RAW-BITS on x86 to use
	  the *-WITH-OFFSET machinery.