Remove usage of auto_ptr in MacroExpander

BUG=angleproject:1269

Change-Id: I1fafa102b065f6da1797e8790ec3ed498d9d8b45
Reviewed-on: https://chromium-review.googlesource.com/339379
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>

src/compiler/preprocessor/MacroExpander.h

@@ -83,7 +83,7 @@ class MacroExpander : public Lexer
     Diagnostics *mDiagnostics;
     bool mParseDefined;
 
-    std::auto_ptr<Token> mReserveToken;
+    std::unique_ptr<Token> mReserveToken;
     std::vector<MacroContext *> mContextStack;
 };