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/indirect_reference_table.cc b/runtime/indirect_reference_table.cc
index 9fbb2e9..c852d5a 100644
--- a/runtime/indirect_reference_table.cc
+++ b/runtime/indirect_reference_table.cc
@@ -18,6 +18,7 @@
 
 #include "base/dumpable-inl.h"
 #include "base/systrace.h"
+#include "java_vm_ext.h"
 #include "jni_internal.h"
 #include "nth_caller_visitor.h"
 #include "reference_table.h"