changes in sbcl-1.4.8 relative to sbcl-1.4.7:
* bug fix: redefinition of method combinations now does the expected thing;
generic functions using that method combination have their effective
methods lazily recomputed according to the new definition of the method
combination. (Reported by Didier Verna at ELS 2018)
* bug fix: :arguments argument to the long form of DEFINE-METHOD-COMBINATION
is now implemented more correctly, supporting suppliedp variables and
&optional defaults. (Reported by Bruno Haible, lp#309084)