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/Sema/SemaTemplate.cpp b/lib/Sema/SemaTemplate.cpp
index c3e3149..61fd826 100644
--- a/lib/Sema/SemaTemplate.cpp
+++ b/lib/Sema/SemaTemplate.cpp
@@ -3036,7 +3036,7 @@
       return TTP->getNumExpansionTemplateParameters();
   }
 
-  return Optional<unsigned>();
+  return None;
 }
 
 /// \brief Check that the given template argument list is well-formed