Directory restructuring of object.h

Break object.h into constituent files.
Reduce number of #includes in other GC header files.
Introduce -inl.h files to avoid mirror files #include-ing each other.
Check invariants of verifier RegTypes for all constructors.

Change-Id: Iecf1171c02910ac152d52947330ef456df4043bc
diff --git a/src/barrier_test.cc b/src/barrier_test.cc
index 284be57..bb7bcb3 100644
--- a/src/barrier_test.cc
+++ b/src/barrier_test.cc
@@ -20,6 +20,7 @@
 
 #include "atomic_integer.h"
 #include "common_test.h"
+#include "mirror/object_array-inl.h"
 #include "thread_pool.h"
 #include "UniquePtr.h"