C1X: implement generic selections

As an extension, generic selection support has been added for all
supported languages.  The syntax is the same as for C1X.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@129554 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/ItaniumMangle.cpp b/lib/AST/ItaniumMangle.cpp
index be17ccf..752163a 100644
--- a/lib/AST/ItaniumMangle.cpp
+++ b/lib/AST/ItaniumMangle.cpp
@@ -1750,6 +1750,7 @@
   case Expr::ChooseExprClass:
   case Expr::CompoundLiteralExprClass:
   case Expr::ExtVectorElementExprClass:
+  case Expr::GenericSelectionExprClass:
   case Expr::ObjCEncodeExprClass:
   case Expr::ObjCIsaExprClass:
   case Expr::ObjCIvarRefExprClass: