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/utils.cc b/runtime/utils.cc
index c332bdf..f26b598 100644
--- a/runtime/utils.cc
+++ b/runtime/utils.cc
@@ -25,7 +25,7 @@
 
 #include <unistd.h>
 
-#include "UniquePtr.h"
+#include "UniquePtrCompat.h"
 #include "base/stl_util.h"
 #include "base/unix_file/fd_file.h"
 #include "dex_file-inl.h"