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/thread.h b/runtime/thread.h
index f7aef42..6d8af51 100644
--- a/runtime/thread.h
+++ b/runtime/thread.h
@@ -21,6 +21,7 @@
 #include <deque>
 #include <iosfwd>
 #include <list>
+#include <memory>
 #include <string>
 
 #include "base/macros.h"
@@ -39,7 +40,6 @@
 #include "stack.h"
 #include "thread_state.h"
 #include "throw_location.h"
-#include "UniquePtrCompat.h"
 
 namespace art {