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/SemaLookup.cpp b/clang/lib/Sema/SemaLookup.cpp
index 940f8f3..9ab3b2d 100644
--- a/clang/lib/Sema/SemaLookup.cpp
+++ b/clang/lib/Sema/SemaLookup.cpp
@@ -731,7 +731,7 @@
     EPI.NumExceptions = 0;
     QualType ExpectedType
       = R.getSema().Context.getFunctionType(R.getLookupName().getCXXNameType(),
-                                            ArrayRef<QualType>(), EPI);
+                                            None, EPI);
 
     // Perform template argument deduction against the type that we would
     // expect the function to have.