Add BOOLEAN-AST-MIXIN as a superclass of fixnum comparison ASTs.
Add BOOLEAN-AST-MIXIN as a superclass of fixnum comparison ASTs.

clasp-developers/SICL,vtomole/SICL,vtomole/SICL,clasp-developers/SICL,vtomole/SICL,vtomole/SICL,clasp-developers/SICL,clasp-developers/SICL