Replace ArrayRef<T>() with None, now that we have an implicit ArrayRef constructor from None

Patch by Robert Wilhelm.

llvm-svn: 181139
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 84aa079..7b332f9 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -6576,9 +6576,7 @@
     EPI.Variadic = true;
     EPI.ExtInfo = FT->getExtInfo();
 
-    QualType R = Context.getFunctionType(FT->getResultType(),
-                                         ArrayRef<QualType>(),
-                                         EPI);
+    QualType R = Context.getFunctionType(FT->getResultType(), None, EPI);
     NewFD->setType(R);
   }