Update LLVM for 3.5 rebase (r209712).

Change-Id: I149556c940fb7dc92d075273c87ff584f400941f
diff --git a/tools/llvm-diff/DifferenceEngine.h b/tools/llvm-diff/DifferenceEngine.h
index 73bf6eb..4470968 100644
--- a/tools/llvm-diff/DifferenceEngine.h
+++ b/tools/llvm-diff/DifferenceEngine.h
@@ -59,7 +59,7 @@
     };
 
     DifferenceEngine(Consumer &consumer)
-      : consumer(consumer), globalValueOracle(0) {}
+      : consumer(consumer), globalValueOracle(nullptr) {}
 
     void diff(Module *L, Module *R);
     void diff(Function *L, Function *R);