Handle AddrLabelExprs in Expr::isConstantExpr

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@55245 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/Expr.cpp b/lib/AST/Expr.cpp
index 9085d2c..a01832f 100644
--- a/lib/AST/Expr.cpp
+++ b/lib/AST/Expr.cpp
@@ -556,6 +556,7 @@
   case ImaginaryLiteralClass:
   case TypesCompatibleExprClass:
   case CXXBoolLiteralExprClass:
+  case AddrLabelExprClass:
     return true;
   case CallExprClass: {
     const CallExpr *CE = cast<CallExpr>(this);