get the protocol more right

Include some generic function arguments for specialization in protocol
functions involving generalizers.  (Otherwise there are some cases where
it's not possible to define methods not in violation of the rules about
specializers applicable to instances of not-standard classes.)

Adjust the CONS-SPECIALIZER example to suit, and include an extra test
case which shows of method-combination as well as the new ability to
have multiple applicable methods with class specializers.