1.0.31.20: smaller code for failing ECASE/ETYPECASE

1.0.31.20: smaller code for failing ECASE/ETYPECASE

(ERROR 'CASE-FAILURE ...) generates a lot of code.  Commonize the code in
a CASE-FAILURE function and have the macros call that function instead.
This change results in fewer entries in the constant vector and smaller
code since fewer arguments have to be loaded.  This makes the error case
slightly slower, but that's not a problem.

Shrinks core size by ~160K on x86-64.