Export dvmIsValid card.

Change-Id: If92998de87db61cad75c7affa1500aed582f9687
diff --git a/vm/alloc/CardTable.h b/vm/alloc/CardTable.h
index 1a6db11..fca6907 100644
--- a/vm/alloc/CardTable.h
+++ b/vm/alloc/CardTable.h
@@ -56,6 +56,11 @@
 void *dvmAddrFromCard(const u1 *card);
 
 /*
+ * Returns true if addr points to a valid card.
+ */
+void dvmIsValidCard(const u1 *card);
+
+/*
  * Set the card associated with the given address to GC_CARD_DIRTY.
  */
 void dvmMarkCard(const void *addr);