Remove object_utils.h.

Break into object_lock, field_helper and method_helper.
Clean up header files following this.
Also tidy some of the Handle code in response to compiler errors when resolving
the changes in this CL.

Change-Id: I73e63015a0f02a754d0866bfaf58208aebcaa295
diff --git a/runtime/mirror/art_method-inl.h b/runtime/mirror/art_method-inl.h
index a5b5df6..01b05a6 100644
--- a/runtime/mirror/art_method-inl.h
+++ b/runtime/mirror/art_method-inl.h
@@ -19,11 +19,13 @@
 
 #include "art_method.h"
 
+#include "class_linker.h"
+#include "dex_cache.h"
 #include "dex_file.h"
 #include "entrypoints/entrypoint_utils.h"
+#include "method_helper.h"
 #include "object-inl.h"
 #include "object_array.h"
-#include "object_utils.h"
 #include "oat.h"
 #include "quick/quick_method_frame_info.h"
 #include "read_barrier-inl.h"