Compatibility layer to transition from UniquePtr to std::unique_ptr.

Use ART_WITH_STLPORT (enabled for the target) to cause the use of UniquePtr,
for the host switch to std::unique_ptr. For now the type remains called
UniquePtr.
Make dalvik compile with clang on the host, move its build to C++11.

Change-Id: I5ba8d2757904bc089ed62047ea03de3c0853fb12
diff --git a/compiler/image_test.cc b/compiler/image_test.cc
index 7c5741b..5a79542 100644
--- a/compiler/image_test.cc
+++ b/compiler/image_test.cc
@@ -27,7 +27,7 @@
 #include "lock_word.h"
 #include "mirror/object-inl.h"
 #include "signal_catcher.h"
-#include "UniquePtr.h"
+#include "UniquePtrCompat.h"
 #include "utils.h"
 #include "vector_output_stream.h"