0.8.0.37:

	Make DEFCONSTANT throw an error of type SB-EXT:DEFCONSTANT-UNEQL
	... rearrange build order so that macros are defined at the
	birth of the cross-compiler (and that relevant variables are
	declared special)
	... define the condition type (slots for OLD-VALUE, NEW-VALUE
	and NAME)
	... actually throw the error in %DEFCONSTANT (and have an ABORT
	restart, too)
	... document and test