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/Basic/SourceManager.cpp b/lib/Basic/SourceManager.cpp
index 550e82c..901d3a6 100644
--- a/lib/Basic/SourceManager.cpp
+++ b/lib/Basic/SourceManager.cpp
@@ -1462,11 +1462,11 @@
 /// in non-performance-critical code.
 static Optional<ino_t> getActualFileInode(const FileEntry *File) {
   if (!File)
-    return Optional<ino_t>();
+    return None;
   
   struct stat StatBuf;
   if (::stat(File->getName(), &StatBuf))
-    return Optional<ino_t>();
+    return None;
     
   return StatBuf.st_ino;
 }