Define and implement CXXNoexceptExpr. Create it in Sema.

llvm-svn: 113623
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 7736581..165dd4d 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -2441,6 +2441,7 @@
   case Expr::CXXScalarValueInitExprClass:
   case Expr::TypesCompatibleExprClass:
   case Expr::UnaryTypeTraitExprClass:
+  case Expr::CXXNoexceptExprClass:
     return NoDiag();
   case Expr::CallExprClass:
   case Expr::CXXOperatorCallExprClass: {