ART: Add object-readbarrier-inl.h

Move some read-barrier code into a new header. This prunes the
include tree for the concurrent-copying collector. Clean up other
related includes.

Test: mmma art
Change-Id: I40ce4e74f2e5d4c692529ffb4df933230b6fd73e
diff --git a/runtime/common_runtime_test.cc b/runtime/common_runtime_test.cc
index 15724a1..01c6641 100644
--- a/runtime/common_runtime_test.cc
+++ b/runtime/common_runtime_test.cc
@@ -39,6 +39,7 @@
 #include "gtest/gtest.h"
 #include "handle_scope-inl.h"
 #include "interpreter/unstarted_runtime.h"
+#include "java_vm_ext.h"
 #include "jni_internal.h"
 #include "mirror/class-inl.h"
 #include "mirror/class_loader.h"