Add heap poisoning support to the entrypoints.

In preparation for full compiler/managed-code support.

Enable stub_test with heap poisoning.

Bug: 12687968
Change-Id: I79fc54ce6386c0a1eb9621759bb4cc23bc393a75
diff --git a/runtime/read_barrier_c.h b/runtime/read_barrier_c.h
index 88bda3a..4f408dd 100644
--- a/runtime/read_barrier_c.h
+++ b/runtime/read_barrier_c.h
@@ -31,6 +31,10 @@
 // #define USE_TABLE_LOOKUP_READ_BARRIER
 #endif
 
+#ifdef ART_HEAP_POISONING
+#define USE_HEAP_POISONING
+#endif
+
 #if defined(USE_BAKER_READ_BARRIER) || defined(USE_BROOKS_READ_BARRIER)
 #define USE_BAKER_OR_BROOKS_READ_BARRIER
 #endif