+;;; 21 = sbcl-0.pre7.62 finally incremented the version after several
+;;; incompatible changes in earlier versions: many many symbols
+;;; renamed, changes in globaldb representation of constants
+;;; and inline functions, and change in the value of
+;;; INTERNAL-TIME-UNITS-PER-SECOND
+;;; 22 = about a zillion changes between sbcl-0.pre7.62 and
+;;; sbcl-0.pre7.133, during which time it seemed too much
+;;; trouble to increment the counter
+;;; 23 = sbcl-0.7.0.1 deleted no-longer-used EVAL-STACK stuff,
+;;; causing changes in *STATIC-SYMBOLS*.
+;;; 24 = sbcl-0.7.1.19 changed PCL service routines which might be
+;;; called from macroexpanded code