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/gc/card_table.cc b/src/gc/card_table.cc
index f27777b..4331270 100644
--- a/src/gc/card_table.cc
+++ b/src/gc/card_table.cc
@@ -19,6 +19,7 @@
 #include <dynamic_annotations.h>
 
 #include "base/logging.h"
+#include "gc/card_table-inl.h"
 #include "heap.h"
 #include "heap_bitmap.h"
 #include "runtime.h"