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/jit/jit.cc b/runtime/jit/jit.cc
index 3631a9d..b32b272 100644
--- a/runtime/jit/jit.cc
+++ b/runtime/jit/jit.cc
@@ -23,6 +23,7 @@
 #include "debugger.h"
 #include "entrypoints/runtime_asm_entrypoints.h"
 #include "interpreter/interpreter.h"
+#include "java_vm_ext.h"
 #include "jit_code_cache.h"
 #include "oat_file_manager.h"
 #include "oat_quick_method_header.h"