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/Analysis/FormatString.cpp b/lib/Analysis/FormatString.cpp
index 10bb9f3..ad0dce4 100644
--- a/lib/Analysis/FormatString.cpp
+++ b/lib/Analysis/FormatString.cpp
@@ -533,7 +533,7 @@
   
   switch (getKind()) {
   default:
-    return Optional<ConversionSpecifier>();
+    return None;
   case DArg:
     NewKind = dArg;
     break;
@@ -766,7 +766,7 @@
     }
   }
 
-  return Optional<LengthModifier>();
+  return None;
 }
 
 bool FormatSpecifier::namedTypeToLengthModifier(QualType QT,