Add read barrier support to the entrypoints.

Also remove "THIS_LOAD_REQUIRES_READ_BARRIER" since reading
an ArtMethod* no longer needs read barrier.

stub_test should also work with read barriers now.

Change-Id: I3fba18042de2f867a18dbdc38519986212bd9769
diff --git a/runtime/oat.h b/runtime/oat.h
index ee2f3f6..29dd76c 100644
--- a/runtime/oat.h
+++ b/runtime/oat.h
@@ -32,7 +32,7 @@
 class PACKED(4) OatHeader {
  public:
   static constexpr uint8_t kOatMagic[] = { 'o', 'a', 't', '\n' };
-  static constexpr uint8_t kOatVersion[] = { '0', '6', '7', '\0' };
+  static constexpr uint8_t kOatVersion[] = { '0', '6', '8', '\0' };
 
   static constexpr const char* kImageLocationKey = "image-location";
   static constexpr const char* kDex2OatCmdLineKey = "dex2oat-cmdline";