[type checker] Implemented type checking of case expressions. It should use a parameterized Generator type but it is not yet supported. Instead, we use GeneratorZZ32 for now. Added bogus IN and = operators for GeneratorZZ32.
[tests] Moved not_working_static_tests/CaseExpr.fss to compiler_tests/Compiled280.fss. compiler_tests/Compiled9.ah.fss is working but compiler_tests/Compiled9.ai.fss is not. It looks like a problem with type checking operator applications.
