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/class_linker_test.cc b/runtime/class_linker_test.cc
index ff90f41..d04f02b 100644
--- a/runtime/class_linker_test.cc
+++ b/runtime/class_linker_test.cc
@@ -16,9 +16,9 @@
 
 #include "class_linker.h"
 
+#include <memory>
 #include <string>
 
-#include "UniquePtrCompat.h"
 #include "class_linker-inl.h"
 #include "common_runtime_test.h"
 #include "dex_file.h"