Use None rather than Optional<T>() where possible.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@175705 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/TemplateBase.cpp b/lib/AST/TemplateBase.cpp
index 520ca25..2b50681 100644
--- a/lib/AST/TemplateBase.cpp
+++ b/lib/AST/TemplateBase.cpp
@@ -229,7 +229,7 @@
   if (TemplateArg.NumExpansions)
     return TemplateArg.NumExpansions - 1;
   
-  return Optional<unsigned>();
+  return None; 
 }
 
 void TemplateArgument::Profile(llvm::FoldingSetNodeID &ID,