Subzero: Change llvm::OwningPtr to C++11's std::unique_ptr.

While I'm at it, normalize the #include order:

1. C++ library headers
2. LLVM headers
3. Subzero headers

A blank line between each group.  Each group sorted alphabetically, case-insensitive.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=3930
R=jfb@chromium.org, jvoung@chromium.org

Review URL: https://codereview.chromium.org/622443002

src/IceTargetLoweringX8632.h

diff --git a/src/IceTargetLoweringX8632.h b/src/IceTargetLoweringX8632.h
index 1533ae3..37f7fef 100644
--- a/src/IceTargetLoweringX8632.h
+++ b/src/IceTargetLoweringX8632.h
@@ -16,11 +16,11 @@
 #ifndef SUBZERO_SRC_ICETARGETLOWERINGX8632_H
 #define SUBZERO_SRC_ICETARGETLOWERINGX8632_H
 
-#include "IceDefs.h"
-#include "IceTargetLowering.h"
 #include "assembler_ia32.h"
+#include "IceDefs.h"
 #include "IceInstX8632.h"
 #include "IceRegistersX8632.h"
+#include "IceTargetLowering.h"
 
 namespace Ice {