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
diff --git a/src/PNaClTranslator.h b/src/PNaClTranslator.h
index 87284fa..464d65b 100644
--- a/src/PNaClTranslator.h
+++ b/src/PNaClTranslator.h
@@ -15,9 +15,10 @@
 #ifndef SUBZERO_SRC_PNACLTRANSLATOR_H
 #define SUBZERO_SRC_PNACLTRANSLATOR_H
 
-#include "IceTranslator.h"
 #include <string>
 
+#include "IceTranslator.h"
+
 namespace Ice {
 
 class PNaClTranslator : public Translator {