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/Support/YAMLParser.cpp b/lib/Support/YAMLParser.cpp
index 2cead20..213f5e1 100644
--- a/lib/Support/YAMLParser.cpp
+++ b/lib/Support/YAMLParser.cpp
@@ -260,7 +260,7 @@
   Token getNext();
 
   void printError(SMLoc Loc, SourceMgr::DiagKind Kind, const Twine &Message,
-                  ArrayRef<SMRange> Ranges = ArrayRef<SMRange>()) {
+                  ArrayRef<SMRange> Ranges = None) {
     SM.PrintMessage(Loc, Kind, Message, Ranges);
   }