Move casts.h and stl_util.h into base/.

Change-Id: Idb3bfa5cec3d146e488031d91265737cde2b4cf4
diff --git a/src/constants_arm.h b/src/constants_arm.h
index 022bc6e..601c572 100644
--- a/src/constants_arm.h
+++ b/src/constants_arm.h
@@ -21,8 +21,8 @@
 
 #include <iosfwd>
 
+#include "base/casts.h"
 #include "base/logging.h"
-#include "casts.h"
 #include "globals.h"
 
 namespace art {