Quick: Fix DCE to mark wide register overlaps correctly.

Previously we missed some cases of overlap with registers
coming from previous blocks.

Bug: 20640451

(cherry picked from commit 83d46ef1eaa8fdecadfdb9564d80e50b42646c37)

Change-Id: I1be879edfbc900b70cee411d9e31e5a4b524530a
diff --git a/compiler/dex/gvn_dead_code_elimination.h b/compiler/dex/gvn_dead_code_elimination.h
index bc75a01..06022db 100644
--- a/compiler/dex/gvn_dead_code_elimination.h
+++ b/compiler/dex/gvn_dead_code_elimination.h
@@ -121,6 +121,7 @@
    private:
     const uint32_t num_vregs_;
     VRegValue* const vreg_data_;
+    BitVector vreg_high_words_;
     ScopedArenaVector<MIRData> mir_data_;
   };