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/reflection_test.cc b/runtime/reflection_test.cc
index 2f70ded..1ba4b7b 100644
--- a/runtime/reflection_test.cc
+++ b/runtime/reflection_test.cc
@@ -23,6 +23,7 @@
 #include "art_method-inl.h"
 #include "base/enums.h"
 #include "common_compiler_test.h"
+#include "java_vm_ext.h"
 #include "jni_internal.h"
 #include "scoped_thread_state_change-inl.h"