0.8.1.43:

0.8.1.43:
	Get SB-MOP:CLASS-PROTOTYPE right in more cases
	... new :PROTOTYPE-FORM property in
		SB-KERNEL:*BUILT-IN-CLASSES* list;
	... use it to generate the prototype in
		SB-PCL::*BUILT-IN-CLASSES*;
	bonus: since this means we have an instance of almost every
	built-in-class by SAVE-LISP-AND-DIE time, we can detect
	longstanding bugs in PURIFY
	... make complex bit-vectors and simple-array-nils purifyable.