Tidy ELF builder.

Don't do "if (ptr)". Use const. Use DISALLOW_COPY_AND_ASSIGN. Avoid public
member variables.
Move ValueObject to base and use in ELF builder.
Tidy VectorOutputStream to not use non-const reference arguments.

Change-Id: I2c727c3fc61769c3726de7cfb68b2d6eb4477e53
diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index fc5b06d..2010e7e 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -20,7 +20,7 @@
 #include "locations.h"
 #include "offsets.h"
 #include "primitive.h"
-#include "utils/allocation.h"
+#include "utils/arena_object.h"
 #include "utils/arena_bit_vector.h"
 #include "utils/growable_array.h"