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/dex/mir_optimization.cc b/compiler/dex/mir_optimization.cc
index 8e8a593..749a235 100644
--- a/compiler/dex/mir_optimization.cc
+++ b/compiler/dex/mir_optimization.cc
@@ -311,7 +311,7 @@
     return true;
   }
   bool use_lvn = bb->use_lvn;
-  UniquePtr<LocalValueNumbering> local_valnum;
+  std::unique_ptr<LocalValueNumbering> local_valnum;
   if (use_lvn) {
     local_valnum.reset(LocalValueNumbering::Create(cu_));
   }