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/gc/accounting/space_bitmap.h b/runtime/gc/accounting/space_bitmap.h
index 6d1ba87..a3073bd 100644
--- a/runtime/gc/accounting/space_bitmap.h
+++ b/runtime/gc/accounting/space_bitmap.h
@@ -54,8 +54,7 @@
   static SpaceBitmap* CreateFromMemMap(const std::string& name, MemMap* mem_map,
                                        byte* heap_begin, size_t heap_capacity);
 
-  ~SpaceBitmap() {
-  }
+  ~SpaceBitmap();
 
   // <offset> is the difference from .base to a pointer address.
   // <index> is the index of .bits that contains the bit representing