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/compiler_ir.h b/compiler/dex/compiler_ir.h
index 70159ca..35d777e 100644
--- a/compiler/dex/compiler_ir.h
+++ b/compiler/dex/compiler_ir.h
@@ -85,8 +85,8 @@
   ArenaAllocator arena;
   ArenaStack arena_stack;  // Arenas for ScopedArenaAllocator.
 
-  UniquePtr<MIRGraph> mir_graph;   // MIR container.
-  UniquePtr<Backend> cg;           // Target-specific codegen.
+  std::unique_ptr<MIRGraph> mir_graph;   // MIR container.
+  std::unique_ptr<Backend> cg;           // Target-specific codegen.
   TimingLogger timings;
 };