Now we have a proper C++ library, use std::unique_ptr.

Also remove the Android.libcxx.mk and other bits of stlport compatibility
mechanics.

Change-Id: Icdf7188ba3c79cdf5617672c1cfd0a68ae596a61
diff --git a/compiler/utils/dedupe_set.h b/compiler/utils/dedupe_set.h
index 7cc253c..4c52174 100644
--- a/compiler/utils/dedupe_set.h
+++ b/compiler/utils/dedupe_set.h
@@ -77,7 +77,7 @@
 
  private:
   std::string lock_name_[kShard];
-  UniquePtr<Mutex> lock_[kShard];
+  std::unique_ptr<Mutex> lock_[kShard];
   std::set<HashedKey, Comparator> keys_[kShard];
 
   DISALLOW_COPY_AND_ASSIGN(DedupeSet);