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_graph.h b/compiler/dex/mir_graph.h
index 85a2d04..778a92d 100644
--- a/compiler/dex/mir_graph.h
+++ b/compiler/dex/mir_graph.h
@@ -979,7 +979,7 @@
   int* i_dom_list_;
   ArenaBitVector** def_block_matrix_;    // num_dalvik_register x num_blocks.
   ArenaBitVector* temp_dalvik_register_v_;
-  UniquePtr<ScopedArenaAllocator> temp_scoped_alloc_;
+  std::unique_ptr<ScopedArenaAllocator> temp_scoped_alloc_;
   uint16_t* temp_insn_data_;
   uint32_t temp_bit_vector_size_;
   ArenaBitVector* temp_bit_vector_;