Revert "comment out the EvaluateAsInt compat code for now"

This reverts commit da9fb5d6, obsoleted by
<http://llvm.org/viewvc/llvm-project?view=revision&revision=347756> "Re-commit
r347417 'Re-Reinstate 347294 with a fix for the failures.'"

compilerplugins/clang/compat.hxx

@@ -157,8 +157,7 @@ inline bool CPlusPlus17(clang::LangOptions const & opts) {
 }
 
 inline bool EvaluateAsInt(clang::Expr const * expr, llvm::APSInt& intRes, const clang::ASTContext& ctx) {
-// this keeps getting landed and then reverted in clang
-#if 0 && CLANG_VERSION >= 80000
+#if CLANG_VERSION >= 80000
     clang::Expr::EvalResult res;
     bool b = expr->EvaluateAsInt(res, ctx);
     if (b && res.Val.isInt())