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/indirect_reference_table.h b/runtime/indirect_reference_table.h
index 833b07a..5015410 100644
--- a/runtime/indirect_reference_table.h
+++ b/runtime/indirect_reference_table.h
@@ -363,9 +363,9 @@
   IRTSegmentState segment_state_;
 
   // Mem map where we store the indirect refs.
-  UniquePtr<MemMap> table_mem_map_;
+  std::unique_ptr<MemMap> table_mem_map_;
   // Mem map where we store the extended debugging info.
-  UniquePtr<MemMap> slot_mem_map_;
+  std::unique_ptr<MemMap> slot_mem_map_;
   /* bottom of the stack */
   mirror::Object** table_;
   /* bit mask, ORed into all irefs */