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/runtime/dex_file.h b/runtime/dex_file.h
index cfa2555..0146f31 100644
--- a/runtime/dex_file.h
+++ b/runtime/dex_file.h
@@ -28,7 +28,7 @@
 #include "mem_map.h"
 #include "modifiers.h"
 #include "safe_map.h"
-#include "UniquePtr.h"
+#include "UniquePtrCompat.h"
 
 namespace art {