Add ArrayRef constructor from None, and do the cleanups that this constructor enables

Patch by Robert Wilhelm.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181138 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AsmParser/LLParser.cpp b/lib/AsmParser/LLParser.cpp
index 998bca5..62d8070 100644
--- a/lib/AsmParser/LLParser.cpp
+++ b/lib/AsmParser/LLParser.cpp
@@ -528,7 +528,7 @@
   if (Result) return false;
 
   // Otherwise, create MDNode forward reference.
-  MDNode *FwdNode = MDNode::getTemporary(Context, ArrayRef<Value*>());
+  MDNode *FwdNode = MDNode::getTemporary(Context, None);
   ForwardRefMDNodes[MID] = std::make_pair(FwdNode, Lex.getLoc());
 
   if (NumberedMetadata.size() <= MID)