Don't include Operator.h from InstrTypes.h.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129271 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/llvm-diff/DifferenceEngine.cpp b/tools/llvm-diff/DifferenceEngine.cpp
index 3cf178e..2344e39 100644
--- a/tools/llvm-diff/DifferenceEngine.cpp
+++ b/tools/llvm-diff/DifferenceEngine.cpp
@@ -14,6 +14,7 @@
 
 #include "DifferenceEngine.h"
 
+#include "llvm/Constants.h"
 #include "llvm/Function.h"
 #include "llvm/Instructions.h"
 #include "llvm/Module.h"