Revert change from auto_ptr to unique_ptr in sample code.

This allows users of the legacy makefile on older systems without
C++11 compiler support to continue using libwebm sample code.

Change-Id: I1dd9487e0d87e355d2394fedb12ec8628a955413

sample.cpp

@@ -115,7 +115,7 @@ int main(int argc, char* argv[]) {
     return -1;
   }
 
-  const std::unique_ptr<seg_t> pSegment(pSegment_);
+  const std::auto_ptr<seg_t> pSegment(pSegment_);
 
   ret = pSegment->Load();
   if (ret < 0) {