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/DiffLog.cpp b/tools/llvm-diff/DiffLog.cpp
index 9cc0c88..5f06a16 100644
--- a/tools/llvm-diff/DiffLog.cpp
+++ b/tools/llvm-diff/DiffLog.cpp
@@ -13,10 +13,9 @@
 
 #include "DiffLog.h"
 #include "DiffConsumer.h"
-
-#include "llvm/Instructions.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/Instructions.h"
 
 using namespace llvm;