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/runtime/dex_method_iterator.h b/runtime/dex_method_iterator.h
index 1975e48..806266d 100644
--- a/runtime/dex_method_iterator.h
+++ b/runtime/dex_method_iterator.h
@@ -140,7 +140,7 @@
   uint32_t class_def_index_;
   const DexFile::ClassDef* class_def_;
   const byte* class_data_;
-  UniquePtr<ClassDataItemIterator> it_;
+  std::unique_ptr<ClassDataItemIterator> it_;
   bool direct_method_;
 };