Sort the #include lines for tools/...

Again, tools are trickier to pick the main module header for than
library source files. I've started to follow the pattern of using
LLVMContext.h when it is included as a stub for program source files.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@169252 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/llvm-diff/DifferenceEngine.h b/tools/llvm-diff/DifferenceEngine.h
index 0246d8f..73bf6eb 100644
--- a/tools/llvm-diff/DifferenceEngine.h
+++ b/tools/llvm-diff/DifferenceEngine.h
@@ -15,11 +15,10 @@
 #ifndef _LLVM_DIFFERENCE_ENGINE_H_
 #define _LLVM_DIFFERENCE_ENGINE_H_
 
+#include "DiffConsumer.h"
+#include "DiffLog.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
-#include "DiffLog.h"
-#include "DiffConsumer.h"
-
 #include <utility>
 
 namespace llvm {