Add more built-in boolean-specific instructions.

code/compiler/13/ast.cpp

@@ -287,6 +287,7 @@ struct case_strategy_bool {
             repr_type repr,
             std::vector<instruction_ptr>& into) {
         branch->expr->compile(env_ptr(new env_offset(1, env)), into);
+        into.push_back(instruction_ptr(new instruction_slide(1)));
     }
 
     size_t case_count(const type* type) {